System for controlling a lateral trajectory of an aircraft including a rudder bar

ABSTRACT

A system for controlling a lateral trajectory of an aircraft includes a rudder bar. Each pedal of the rudder bar is movable between a neutral position (p n ) and an end-of-travel position (p f ) along a unique travel. A movement of the pedal between the neutral position (p n ) and an activation position (p act ) commands a lateral movement by actuating a lateral movement device of a first set including a nose gear wheel, the different braking of the aircraft being nonactive. A movement of the pedal from the activation position (p act ) to the end-of-travel position (p f ) commands a lateral movement by actuating a device of the first set and the differential braking. A haptic feedback generator applies a first haptic profile to each pedal between the neutral position (p n ) and the activation position (p act ) and a second haptic profile from the activation position (p act ) toward the end-of-travel position (p f ).

The present disclosure relates to a system for controlling a lateraltrajectory of an aircraft rolling on a runway, the aircraft including:

-   -   a first set of actionable lateral movement devices, including a        steerable front wheel, and    -   a differential braking assembly of a main landing gear, the        differential braking assembly being configured in order, in an        active state, to the exclusion of a nonactive state, to generate        a movement of the aircraft around a yaw axis,

the control system including a rudder bar able to be actuated by apilot, the rudder bar including a left pedal and a right pedal.

BACKGROUND

The driving of an aircraft on the ground, and in particular the controlof the aircraft around its yaw axis, is generally provided bycontrolling the steering angle of the nose gear wheel, by theorientation of the rudder, and in addition by a differential brakingassembly able to exert a braking differential between a left mainlanding gear and the right main landing gear to generate the yawmovement. The control of the aircraft around its yaw axis may further bedone using electric motors driving the wheels of the main landing gear,at different speeds and/or by applying a thrust differential between theleft engine and the right engine.

Various control means are known to command these different lateralmovement devices.

In particular, some aircraft include three separate control means eachacting on one of the aforementioned lateral movement devices. Thesecontrol means for example consist of a tiller, a rudder bar andindependent brake pedals.

The tiller is a control wheel whose rotation makes it possible to causea corresponding modification of the steering angle of the wheel.

The rudder bar is intended to control the rudder. In particular, therudder bar generally includes a left pedal, the movement of which isintended to control a left turn, and a right pedal, the movement ofwhich is intended to control a right turn.

The brake pedals include a left brake pedal and a right brake pedal, theactuation of which is intended to command braking of the left or rightmain landing gear, respectively, therefore a turn to the left or to theright, respectively.

The brake pedals are for example mounted on the rudder bar. Thus, eachrudder bar pedal is movable along a first degree of freedom, for examplein translation, associated with a command of the rudder, and along asecond degree of freedom, for example in rotation around an axisorthogonal to the translation direction of the pedal, associated with acommand of the differential braking assembly.

Alternatively, it has been proposed to include the control of thesteering angle of the nose gear wheel in the rudder bar.

These solutions may be subject to improvement.

In particular, the simultaneous management of the control orders to beissued via the rudder bar and those to be issued by actuating the tilleror the brake pedals induces a substantial workload for the pilot.

Furthermore, such a control system leaves the pilot complete latitudefor the use of the various lateral movement devices.

Yet under certain circumstances, using the differential braking assemblymay have drawbacks, and may in particular prove uncomfortable for thepassengers of the aircraft or cause heating of the braking devicesleading to damage.

Furthermore, when the brake pedals are mounted on the rudder bar, themovements of the pedals along both degrees of freedom are not coupled,such that actuating only the differential braking assembly to apply agiven braking force differential, only the rudder to steer said rudderat a given angle, and simultaneously actuating the differential brakingassembly and the rudder may prove difficult and imprecise, and thereforegenerate a substantial workload for the pilot.

One aim of the invention therefore consists of providing a system forcontrolling a lateral trajectory of an aircraft generating a minimalworkload for the pilot, while minimizing the risks related to using thedifferential braking assembly.

To that end, the invention relates to a control system of theaforementioned type, characterized in that each of the left and rightpedals can be moved between the neutral position and an end-of-travelposition along a single preset travel, a movement of the left pedal,respectively of the right pedal, along said preset travel, between theneutral position and a predetermined differential braking activationposition, being intended to command a movement of the aircraft aroundthe yaw axis along a first direction, respectively a second directionopposite the first direction, by actuation of at least one movementdevice of the first assembly, the differential braking assembly beingnonactive, a movement of the left pedal, respectively of the rightpedal, along said preset travel, from the differential brakingactivation position toward the end-of-travel position being intended tocommand a movement of the aircraft around the yaw axis along the firstdirection, respectively the second direction, by actuation of at leastone movement device of the first assembly, and by actuation of thedifferential braking assembly, the differential braking assembly beingactive, and in that the rudder bar includes a haptic feedback generatorconfigured to apply, to each of the left and right pedals, a firsthaptic profile when the left, respectively right, pedal is moved fromthe neutral position to the activation position, and a second hapticprofile, distinct from the first haptic profile, when the left,respectively right pedal is moved from the activation position to theend-of-travel position.

The control system according to the invention may comprise one or moreof the following features, considered alone or according to anytechnically possible combination:

-   -   the haptic feedback generator is configured to apply, to each of        the left and right pedals, a force opposing the actuation of the        pedal according to a first force profile when the left,        respectively right, pedal is moved from the neutral position to        the activation position, and according to a second force        profile, distinct from the first force profile, when the left,        respectively right pedal is moved from the activation position        to the end-of-travel position.    -   the haptic feedback generator is configured to apply, to each of        the left and right pedals, a force opposing the actuation of the        pedal, such that the first derivative of the force opposing the        actuation of the pedal from the activation position to the        end-of-travel position is strictly greater than the first        derivative of the force opposing the actuation of the pedal to        the activation position.    -   the first derivative of the force opposing the actuation of the        pedal from the differential braking activation position to the        end-of-travel position is strictly greater than any first        derivative of the force opposing the actuation of the pedal from        the neutral position to the differential braking activation        position.    -   said preset travel is a movement of said pedal chosen from        among: a translational movement, in particular a straight or        circular translational movement, and a rotational movement.    -   each of the left and right pedals is further movable between a        rear position and the neutral position, the neutral position        being between the rear position and the end-of-travel position,        and in that the system includes a mechanism for coupling the        movement of the left and right pedals, configured, when the left        pedal, respectively the right pedal, is moved toward the        end-of-travel position, to drive a movement of the right pedal,        respectively of the left pedal, toward the rear position.    -   said preset travel is a movement of said pedal according to a        single degree of freedom.    -   the differential braking activation position is a preset fixed        position of the pedal along said preset travel.    -   the control system includes a regulating module, configured to        determine a threshold value of a trajectory parameter at least        at one moment during the movement of the aircraft on the ground,        as a function of at least one criterion chosen from among a        piece of information relative to the current speed of the        aircraft, a current runway state, an operating state of the nose        gear wheel and a temperature of braking devices of the        differential braking assembly, the threshold value being        representative of a first limit trajectory able to be reached by        the aircraft by actuating at least one lateral movement device        of the first assembly, the differential braking assembly being        nonactive.    -   the haptic feedback generator is configured to determine the        activation position as a function of said threshold value, and        to determine the first and second haptic profiles as a function        of said activation position.    -   the control system comprises a device for acquiring a current        position of said left pedal and a current position of said right        pedal, said positions being representative of an instruction        lateral trajectory.    -   the control system includes a trajectory control module        configured to, selectively:        -   if none of the current positions of the left and right            pedals are between the activation position and the            end-of-travel position, send at least one input instruction            to at least one lateral movement device of the first set, to            the exclusion of the differential braking assembly, said            input instruction being configured to create, when it is            applied to the lateral movement devices of the first set,            the differential braking assembly being nonactive, a lateral            movement of the aircraft according to or tending toward the            instruction lateral trajectory,        -   if the current position of the left pedal or right pedal is            between the activation position and the end-of-travel            position, send input instructions to at least one lateral            movement device of the first set and the differential            braking assembly, said input instructions being configured            to create, when they are applied to the lateral movement            device of the first set and the differential braking            assembly, a lateral movement of the aircraft according to or            tending toward the instruction lateral trajectory.    -   the differential braking assembly includes a braking device of a        left main landing gear and a braking device of a right main        landing gear, the differential braking assembly being configured        in order, in the active state, to the exclusion of the nonactive        state, to exert, at a given moment, a left braking force on the        left main landing gear and a right braking force, distinct from        the right braking force, on the right main landing gear, in        order to generate a movement of the aircraft around the yaw        axis.    -   the lateral movement devices further include a set of electric        motors configured in order, in an active state, to the exclusion        of a nonactive state, to apply a speed differential between the        left main landing gear and a right main landing gear to generate        a movement of the aircraft around the yaw axis, the movement of        the left pedal, respectively of the right pedal, between the        neutral position and the differential braking activation        position is intended to command the movement of the aircraft        around the yaw axis by actuating at least one movement device of        the first assembly, the differential braking assembly and the        set of electric motors being nonactive, and the movement of the        left pedal, respectively of the right pedal, from the        differential braking activation position toward the        end-of-travel position is intended to command the movement of        the aircraft around the yaw axis by actuation of at least one        movement device of the first assembly, and by actuation of the        differential braking assembly and the set of electric motors,        the differential braking assembly and the set of electric motors        being active.    -   the control system includes a module for determining ground        trajectories of the aircraft, configured to determine, at least        at one moment:        -   a current trajectory of the aircraft on the ground,            including a series of waypoints predicted for at least one            element of the aircraft, under unchanged conditions of the            lateral movement devices of the set and the differential            braking assembly,        -   at least a first limit trajectory, including a series of            first limit waypoints that may be reached by the element of            the aircraft by actuating the left pedal and/or the right            pedal between the neutral position and the differential            braking activation position,        -   at least a second limit trajectory, including a series of            second limit waypoints that may be reached by the element of            the aircraft by actuating the left pedal or the right pedal            between the differential braking activation position and the            end-of-travel position, and the control system includes a            display assembly comprising:        -   a viewer, configured to display a view of a runway portion            located near the aircraft;        -   a display generating module, configured to display, on the            viewer, a current trajectory curve representative of said            current trajectory, at least a first limit curve            representative of the first limit trajectory, and at least a            second limit curve representative of the second limit            trajectory, said curves being superimposed on the view of            the portion of the runway.

BRIEF SUMMARY OF THE DRAWINGS

The invention will be better understood upon reading the followingdescription, provided solely as an example and done in reference to theappended drawings, in which:

FIG. 1 schematically shows an aircraft including a control systemaccording to one embodiment;

FIG. 2 schematically shows a nose gear wheel of the aircraft of FIG. 1;

FIG. 3 is a diagram illustrating the movement devices of the aircraft ofFIG. 1 and the control means of these devices;

FIG. 4 is a diagram of a control system according to one embodiment ofthe invention;

FIG. 5 is a graph schematically illustrating the ratio variation of thelateral force exerted on a nose gear wheel based on the sideslip anglefor different runway states and for a given vertical force;

FIG. 6 is a diagram of a manual command device of the control system ofFIG. 4, according to one particular embodiment;

FIG. 7 schematically illustrates a force profile applied by a hapticfeedback generator of the system of FIG. 4;

FIG. 8 schematically illustrates a control module of the control systemof FIG. 4 according to one particular embodiment of the invention;

FIGS. 9 and 10 are diagrams illustrating conditions for displayingcurrent and limit trajectory curves on a viewer;

FIGS. 11 to 16 illustrate different modes for depicting trajectorycurves on a viewer;

FIG. 17 illustrates a method for controlling a trajectory according to afirst aspect; and

FIG. 18 illustrates a method for controlling a trajectory according to asecond aspect.

DETAILED DESCRIPTION

FIG. 1 shows an aircraft 1 rolling on the ground on a runway 3. Theaircraft 1 is mobile in a longitudinal direction and around a yaw axisZ₁-Z₁.

FIG. 1 also shows the roll axis X₁-X₁ of the aircraft 1 and the pitchaxis Y₁-Y₁ of the aircraft 1.

Hereinafter, “longitudinal” will refer to an axis or a directionparallel to the direction of elongation of the aircraft 1.

The yaw axis Z₁-Z₁ is an axis orthogonal to the longitudinal direction,contained in the plane of symmetry of the aircraft 1 and passing throughthe center of gravity of the aircraft 1.

By extension, “vertical” will refer to an axis or a direction parallelto the yaw axis Z₁-Z₁.

Furthermore, “lateral” will refer to an axis or a direction orthogonalto the yaw axis Z₁-Z₁ and the longitudinal direction.

Moreover, “longitudinal plane” will refer to a plane orthogonal to theyaw axis Z₁-Z₁, and “vertical plane” to a plane orthogonal to thelongitudinal plane.

The aircraft 1 is able to move, at each moment, along a ground speedvector Vs. The projection of this speed vector Vs over a planeorthogonal to the yaw axis Z₁-Z₁ forms, with the longitudinal directionof the aircraft, an angle referred to hereinafter as yaw angle λ.

Hereinafter, “angle” will refer to an angle oriented in thecounterclockwise direction seen from above.

The aircraft 1 includes a nose gear 5, referred to hereinafter as nosegear wheel, and a main landing gear 7 comprising a left main landinggear 7 a and a right main landing gear 7 b. Typically, the nose gear 5,the left main landing gear 7 a and the right main landing gear 7 b eachinclude two wheels.

The nose gear wheel 5 and the main landing gear 7 are in contact withthe runway 3 when the aircraft 1 moves on the ground on the runway.

The nose gear wheel 5 is able to roll in a front rolling directionD_(R), and to move, in a longitudinal plane, according to a wheel speedvector V_(R) (FIG. 2). The front rolling direction D_(R) forms, with thelongitudinal direction of the aircraft, an angle δ_(dr) referred tohereinafter as “steering angle”.

The front rolling direction D_(R) further forms, with the wheel speedvector V_(R), a nose gear sideslip angle denoted 136 (FIG. 2). The nosegear sideslip angle 136 is nil when the front rolling direction isparallel to the wheel speed vector V_(R).

The nose gear wheel 5 is symmetrical along a vertical plane parallel tothe rolling direction, hereinafter called “plane of the nose gearwheel”.

The nose gear wheel 5 is rotatable around a vertical axis. The nose gearwheel 5 is further steerable. In particular, the nose gear wheel 5 isprovided with a steering device 9 of the wheel 5, configured to changethe steering angle δ_(dr) of the wheel 5.

The left 7 a and right 7 b main landing gears are each stationaryrelative to the aircraft 1.

The left 7 a and right 7 b main landing gears are able to roll along amain rolling direction. The main rolling direction forms, with theground speed vector Vs of the aircraft, a main landing gear sideslipangle βT.

The aircraft 1 includes longitudinal movement devices 11 and lateralmovement devices 13.

These movement devices are illustrated schematically in FIG. 3.

The longitudinal movement devices 11 are intended to control themovement of the aircraft 1 on the ground along the longitudinaldirection of the aircraft. The lateral movement devices 13 are intendedto control the movement of the aircraft on the ground along a lateraldirection, around the yaw axis Z₁-Z₁.

The longitudinal movement devices 11 are able to exert a longitudinalforce on the aircraft, oriented toward the front or rear of the aircraft1, to drive a movement of the aircraft along the longitudinal directionof the aircraft or to oppose such a movement.

Typically, the longitudinal movement devices include a motor assembly 15and braking devices 17.

The motor assembly 15 for example includes motors 19 able to exert athrust force on the aircraft 5, such as reactors, turboprops orturbines, and a device 21 for controlling the motors 19. For example,the motors 19 include a left motor and a right motor.

According to one embodiment, the motor assembly 15 further includes aset of electric motors 23 able to drive the movement of the main landinggear 7, provided with a device 25 for controlling these electric motors.

The set of electric motors 23 in particular includes a left electricmotor 23 a capable of moving the left main landing gear 7 a, and a rightelectric motor 23 b, capable of moving the right main landing gear 7 b.

The device 25 for controlling the electric motors is configured tocommand the left electric motor 23 a and the right electric motor 23 bsymmetrically, so as to drive the movement of the left main landing gear7 a according to a left main landing gear speed VTa and to drive themovement of the right main landing gear 7 b according to a right mainlanding gear speed VTb=VTa, and thus to generate a longitudinal movementof the aircraft.

The braking devices 17 include a braking assembly 27 of the main landinggear, provided with a control device 29.

The braking assembly 27 includes a braking device 27 of the left mainlanding gear and a braking device 27 b of the right main landing gear.

The control device 29 is configured to command the braking devices 27 a,27 b symmetrically so as to exert, on the left main landing gear 7 a andthe right main landing gear 7 b, a same force FTa=FTb opposing themovement of the left 7 a and right 7 a main landing gears and thus togenerate a longitudinal force opposing the longitudinal movement of theaircraft.

The lateral movement devices 13 are configured to set the aircraft 1 inmotion around the yaw axis Z₁-Z₁, according to a positive angle (i.e.,to the left) or a negative angle (i.e., to the right).

The lateral movement devices 13 are thus configured to modify thelateral trajectory of the aircraft, i.e., the trajectory of the aircraftalong a direction orthogonal to the roll axis X1-X1 of the aircraft.

In particular, the movement devices are configured to modify the yawangle λ of the aircraft.

Hereinafter, “lateral movement” will refer to a movement around the yawaxis Z₁-Z₁, combined with a movement in the longitudinal direction.

The lateral movement devices 13 are able to be actuated, i.e., have atleast one operating parameter able to be modified to generate a movementof the aircraft 1 around the yaw axis Z₁-Z₁.

An actuation of a lateral movement device 13 therefore includes changingan operating parameter of said device capable of modifying the lateraltrajectory of the aircraft, for example capable of modifying the curveradius of said trajectory and the yaw angle λ of the aircraft.

The lateral movement devices 13 include first 13 a and second 13 b setsof lateral movement devices.

The first set 13 a in particular includes the device 9 for steering thewheel 5, capable of changing the steering angle δdir of the nose gearwheel 5 in order to modify the lateral trajectory of the aircraft.

The first set 13 a further includes a steerable rudder 31, provided witha steering device 33. The steering device 33 is able to change theorientation δn of the rudder 31 to modify the lateral trajectory of theaircraft.

The second set 13 b includes the braking assembly 27, commanded by thecontrol device 29 of the braking assembly.

Indeed, the control device 29 of the braking assembly is configured tocommand the braking device 27 a of the left main landing gear and thebraking device 27 b of the right main landing gear asymmetrically, so asto exert a non-nil force differential ΔF between the left 7 a and right7 b main landing gears, and thus to set the aircraft 1 in motion aroundthe yaw axis, in order to modify its lateral trajectory.

In particular, the control device 29 of the braking assembly isconfigured to command the braking device 27 a of the left main landinggear 7 a and the braking device 27 b of the right main landing gear 7 b,so as to exert, at a given moment, on the left main landing gear 7 a, aleft braking force FTa′, and to exert, on the right main landing gear 7b, a right braking force FTb′=FTa′+/−ΔF.

Such asymmetrical braking is able to cause the aircraft 1 to move aroundthe yaw axis in a positive direction (when FTa′>FTb′) or in a negativedirection (when FTb′<FTb′).

For example, one of the braking forces FTa′ or FTb′ is nil.

The braking assembly 27, when implemented to generate a lateralmovement, will hereinafter be called differential braking assembly 27′.

The differential braking assembly 27′ may be active or inactive.

In the active state, the differential braking assembly 27′ is able togenerate a lateral movement of the aircraft 1.

Indeed, in the active state, the differential braking assembly 27′ iscapable of exerting a distinct left braking force and right brakingforce, i.e., a non-nil differential force ΔF between the left 7 a andright 7 b main landing gears, so as to generate the lateral movement ofthe aircraft 1.

In the inactive state, the differential braking assembly 27′ is capableof exerting only an equal left braking force and right braking force,optionally nil, and therefore does not generate any lateral movement ofthe aircraft 1.

The differential braking assembly 27′ is able to be activated, i.e.,configured in the active state, or deactivated, i.e., configured in theinactive state.

According to one particular embodiment, the second assembly 13 b furtherincludes the set of electric motors 23, controlled by the control device25 of the electric motors.

Indeed, the control device 25 of the motors is configured to command theleft electric motor 23 a and the right electric motor 23 basymmetrically so as to apply a speed differential ΔVT between the left7 a and right 7 b main landing gears, and thus to set the aircraft 1 inmotion around the yaw axis.

Thus, the device 25 for controlling the motors is configured to command,at a given moment, the left electric motor 23 a so as to drive themovement of the left main landing gear 7 a according to a left mainlanding gear speed VTa′ and the right electric motor 23 b so as to drivethe movement of the right main landing gear 7 b according to a rightmain landing gear speed VTb′=VTa′+/−ΔVT.

The set of electric motors 23, when implemented to generate a lateralmovement, will hereinafter be called differential motor assembly 23′.

The differential motor assembly 23′ may be active or inactive.

In the active state, the differential motor assembly 23′ drives themotion of the left 7 a and right 7 b main landing gears according to aleft main landing gear speed VTa and a right main landing gear speedVTb≠VTa that are different, so as to generate a lateral movement of theaircraft 1.

In the inactive state, the differential motor assembly 23′ drives themotion of the left 7 a and right 7 b main landing gears according toequal speeds, and therefore does not generate any lateral movement ofthe aircraft 1.

According to an alternative that is not shown, the second assembly 13 bfurther includes the motor assembly 15. Indeed, the control device 21 ofthe motors 19 is configured to command the left motor and the rightmotor asymmetrically so as to apply a thrust differential between theleft and right motors, and thus to set the aircraft 1 in motion aroundthe yaw axis.

Hereinafter, actuating a lateral movement device will refer to changingat least one setting of said device, for example changing the steeringangle of the nose gear wheel 5, the orientation of the rudder 31,applying a given force differential between the left main landing gear 7a and the right main landing gear 7 b, or applying a speed differentialbetween the left main landing gear 7 a and the right main landing gear 7b.

The aircraft 1 further includes an assembly 35 for determiningparameters relative to the movement of the aircraft on the ground.

These parameters include a current position of the aircraft 1 on therunway, as well as parameters relative to the movement of the aircraft1, in particular:

-   -   the ground speed vector V_(S) of the aircraft (hereinafter        ground speed vector) as well as the components Vx, Vy and Vz of        the speed vector V_(S) in a local land coordinate system (X₀,        Y₀, Z₀);    -   the modulus |V_(S)| of this speed vector;    -   the yaw speed r of the aircraft, i.e., the angular movement        speed of the aircraft around its yaw axis Z;    -   the orientation of the axes of the aircraft relative to the        local land coordinate system, i.e., the angle φ between the        pitch axis Y₁-Y₁ of the aircraft 1 and the horizontal reference        plane X₀-Y₀ of the land coordinate system, the angle θ between        the roll axis X₁-X₁ of the aircraft 1 and the horizontal        reference plane X₀-Y₀, and the angle ψ between the roll axis        X₁-X₁ of the aircraft 1 and the vertical reference plane X₀-Z₀        of the land coordinate system;    -   the lateral acceleration of the aircraft ay;    -   a sideslip angle βkp of the aircraft 1 at least at one point P        of the aircraft 1.

To that end, the determining assembly 35 for example includes ageographical position sensor, such as a satellite position sensor, forexample a GPS sensor and an inertial unit.

These parameters further include operating parameters of the aircraft 1.

In particular, the determining assembly 35 is configured to determine anoperating state of the nose gear wheel 5, and to detect any failure ormalfunction of the nose gear wheel 5 that may prevent the control of thesteering angle of the nose gear wheel 5. In case of failure, the nosegear wheel 5 generally rotates freely, but its steering angle may nolonger be commanded by the orientation device 9.

The determining assembly 35 is also configured to determine the currenttemperature of the braking devices 27 a, 27 b.

According to one embodiment, these parameters may include estimatedenvironmental parameters, in particular a runway state (for example dry,wet or icy runway).

These parameters further include a current state of the lateral movementdevices, in particular:

-   -   A current steering angle δdir of the nose gear wheel 5,    -   A current orientation angle δn of the rudder 31,    -   A braking command differential between the left 7 a and right 7        b main landing gears,    -   A speed command differential of the electric motors 23 a, 23 b        between the left and right main landing gears,    -   A thrust command differential between the left and right motors.

The aircraft 1 is provided with a system 40 for controlling the lateraltrajectory of the aircraft 1 on the ground, one embodiment of which isillustrated schematically in FIG. 4.

The control system 40 is configured to acquire a lateral trajectoryorder, and to control the lateral movement devices 13 such that theaircraft 1 follows the acquired lateral trajectory.

A lateral trajectory refers to a trajectory described by at least onepoint or element of the aircraft 1, combining a longitudinal movementand a lateral movement.

The considered point or element of the aircraft 1 is for example thecenter of gravity of the aircraft 1, the nose of the aircraft 1, thenose gear wheel 5, the end of the wing this or the tail of the aircraft1.

A lateral trajectory is characterized, at each point of said trajectory,by a lateral movement direction (i.e., to the left or to the right), andby at least one lateral trajectory parameter, for example:

-   -   a curve radius ρ, preferably associated with speed information        at that point, in particular the modulus |V_(S)| of the speed        vector at that point, and/or    -   a yaw speed r at that point.

The control system 40 is further configured to determine a currenttrajectory of the aircraft and limit trajectories achievable by theaircraft, and to command the display of said trajectories on a viewer,intended for the pilot.

To that end, the control system 40 includes several modules, groupedtogether hereinafter into functional assemblies.

In particular, the control system 40 includes a regulating assembly 48,a command assembly 50 of the lateral trajectory, a control assembly 52of the lateral trajectory, and a display assembly 54.

The regulating assembly 48 is configured to determine regulatingparameters of the lateral movement devices 13.

In particular, the regulating assembly 48 is configured to determine asteering angle range of the nose gear wheel, denoted [δdir_(min);δdir_(max)], outside which a risk of loss of adhesion of the nose gearwheel 5 is significantly increased.

The regulating assembly 48 is further intended to regulate the use ofthe differential braking assembly 27′, in particular to determine anactivation threshold of the differential braking assembly 27′, inparticular a first limit trajectory from which the differential brakingassembly 27′ must be activated.

The regulating assembly 48 is further configured to determine a secondlimit trajectory achievable by the aircraft 1 by using lateral movementdevices 13, in particular the differential braking assembly 27′.

The regulating assembly 48 is further able to determine a currenttrajectory of the aircraft 1.

The command assembly 50 is configured to acquire a lateral trajectoryorder.

In the illustrated example, the command assembly 50 is configured toacquire a lateral trajectory order, or input or instruction lateraltrajectory, entered by a pilot.

Alternatively, the command assembly 50 is configured to acquire alateral trajectory order generated by an automatic pilot.

The control assembly 52 of the lateral trajectory is configured tocontrol the lateral movement devices 13 such that the aircraft 1 followsan instruction lateral trajectory according to the lateral trajectoryorder acquired by the command assembly 50.

In particular, the control assembly 52 is configured to determine, fromthe trajectory order, instruction orders to be applied to one or severalof the lateral movement devices 13 so that the aircraft 1 follows theinstruction lateral trajectory, and to send these instruction orders tothe lateral movement devices 13.

In particular, the control assembly 52 is configured to determine theinstruction orders such that the steering angle of the nose gear wheel 5remains in the steering angle range of the nose gear wheel [δdir_(min);δdir_(max)], beyond which a risk of loss of adhesion of the nose gearwheel 5 is significantly increased.

The display assembly 54 is configured to display, for the pilot, a viewof at least one runway portion on which the aircraft moves, as well as acurve representative of the current trajectory of the aircraft 1, and atleast one limit curve representative of a limit trajectory able to beachieved by at least one element of the aircraft by actuating at leastone lateral movement device, said curves being superimposed on the viewof the runway portion.

As described below, the display assembly is for example configured todisplay a first limit curve representative of the first limit trajectoryand a second limit curve representative of the second limit trajectory,superimposed on the view of the runway portion.

In the illustrated embodiment, the regulating assembly 48 includes amodule 58 for limiting the steering angle of the nose gear wheel 5.

The regulating assembly 48 further includes a regulating module 60 forthe differential braking assembly 27′.

The regulating assembly 48 also includes a module 62 for determiningtrajectories.

The limiting module 58 is configured to determine the steering anglerange of the nose gear wheel, denoted [δdir_(min); δdir_(max)], outsidewhich a risk of loss of adhesion of the nose gear wheel 5 issignificantly increased.

The limiting module 58 is configured to determine or receive informationrelative to the current ground speed of the aircraft and at least onemaximum authorized sideslip angle of the nose gear wheel 5, denotedβδmax, and/or a maximum authorized sideslip angle of the left and rightmain landing gears 7 a, 7 b, denoted βTmax.

The information relative to the current ground speed of the aircraft forexample includes the modulus |V_(S)| of the current ground speed vectorof the aircraft 1, and the current yaw speed r of the aircraft 1.

The limiting module 58 is in particular configured to receive this speedinformation from the determining assembly 35.

Preferably, the limiting module 58 is also configured to estimate orreceive a parameter representative of a current adhesion state of therunway. This adhesion state is for example a dry state, corresponding tomaximum adhesion, a wet state, corresponding to medium adhesion, or anicy state, corresponding to low adhesion. For example, the limitingmodule 58 is configured to receive this adhesion state parameter fromthe control tower on the ground.

Preferably, the limiting module 58 is configured to extract the maximumauthorized sideslip angle βδmax of the nose gear wheel 5 and, ifapplicable, the maximum authorized sideslip angle βTmax of the left andright main landing gears 7 a, 7 b, from a database.

The limiting module 58 thus includes a database of maximum sideslipangles. This database includes predetermined maximum authorized sideslipangle values of the nose gear wheel 5 and/or left 7 a and right 7 b mainlanding gears.

The maximum sideslip angle βδmax of the nose gear wheel 5 is thesideslip angle βδ of said wheel 5 beyond which a risk of loss ofadhesion of the tire of the wheel 5 is significantly increased.

Preferably, the database includes predetermined maximum authorizedsideslip angle values of the nose gear wheel 5 and/or left 7 a and right7 b main landing gears as a function of the current runway state.

The maximum sideslip angle βδmax of the nose gear wheel 5 is thenpreferably the sideslip angle βδ of said wheel 5 beyond which a risk ofloss of adhesion of the tire of the wheel 5 is significantly increasedin light of the runway state.

FIG. 5 thus shows the variation of the lateral force coefficient Kyexerted on the nose gear wheel 5 as a function of the sideslip angle βδ,for different runway states (dry, wet or icy runway) and for a givenvertical force Fz.

The lateral force Fy exerted on the nose gear wheel 5 may be expressedby:F _(y) =F _(Z) *K _(y)(βδ)where F_(z) is the vertical force and Ky is the lateral forcecoefficient, which is a function of the sideslip angle βδ.

The slope efficiency or adhesion coefficient μ_(y) are also defined,corresponding to the derivative of the lateral force relative to thesideslip angle:

${\mu_{y}({\beta\delta})} = {\frac{{dK}_{y}}{d\;\beta\;\sigma}({\beta\delta})}$

FIG. 5 shows two successive states:

-   -   a linear state, obtained while the sideslip angle βδ remains        below a threshold value βδ₀, in which the lateral force        coefficient Ky is a substantially linear function of the        sideslip angle βδ. In the linear state, the adhesion coefficient        μ_(y) is substantially constant or increasing.    -   a downgraded state, obtained when the sideslip angle β exceeds        the threshold value βδ₀, in which the lateral force coefficient        Ky is no longer a linear function of the sideslip angle. In the        illustrated example, the lateral force coefficient Ky is        saturated beyond the sideslip angle threshold value, but it may        also decrease. In the downgraded state, the adhesion coefficient        μ_(y) is thus a nil or decreasing function of the sideslip angle        βδ. When the downgraded state is reached, a risk of loss of        adhesion and breaking away of the nose gear wheel 5 exists.

Preferably, the maximum authorized sideslip angle βδmax of the nose gearwheel 5 is equal to the sideslip angle βδ₀ threshold value.

Alternatively, the maximum authorized sideslip angle βδmax is below thethreshold value, for example between the threshold value βδ₀ and90%*βδ₀.

Likewise, the maximum sideslip angle βTmax of the left 7 a and right 7 bmain landing gears is the sideslip angle β of these main landing gearsbeyond which a risk of loss of adhesion of the tire of the wheel 5 issignificantly increased. Preferably, the maximum authorized sideslipangle βTmax of the left and right main landing gears is equal to thesideslip angle threshold value βT₀ beyond which a downgraded state isreached.

Alternatively, the maximum authorized sideslip angle βmax is below thethreshold value, for example between the threshold value βT₀ and90%*βT₀.

The database of maximum sideslip angles thus includes, for each runwaystate, at least one maximum authorized sideslip angle value βδmax of thenose gear wheel 5 and at least one maximum authorized sideslip anglevalue βTmax of the left 7 a and right 7 b main landing gears.

Preferably, as described above, the limiting module 58 is configured toestimate or receive a parameter representative of a current adhesionstate of the runway and to extract, from the database, the maximumauthorized sideslip angle(s) βδmax and/or βTmax as a function of saidparameter.

According to one alternative, the limiting module 58 is configured toestimate one or more maximum authorized sideslip angle(s) βδmax and/orβTmax independently of the runway adhesion state.

The limiting module 58 is further configured to determine, as a functionof information relative to the current speed of the aircraft, themaximum authorized sideslip angle βδmax of the nose gear wheel 5, andthe maximum authorized sideslip angle βTmax of the left 7 a and right 7b main landing gears, the steering angle range [δdir_(min); δdir_(max)]of the nose gear wheel 5.

The steering angle range [δdir_(min); δdir_(max)] of the nose gear wheel5 is determined such that, when the steering angle of the nose gearwheel 5 is within said steering angle range, the sideslip angle βδ ofthe nose gear wheel 5 is lower, in absolute value, than the maximumsideslip angle βδmax.

The steering angle range [δdir_(min); δdir_(max)] of the nose gear wheel5 is for example determined from a simplified model, called “bicyclemodel”, in which the left 7 a and right 7 b main landing gears arelikened to a virtual landing gear located in the longitudinal plane ofsymmetry of the aircraft 1, the nose gear wheel 5 retaining itssteerable wheel role.

According to this model, the steering angle δdir of the wheel 5, thecurrent sideslip angle βδ of the wheel 5 and the current sideslip angleβT of the main landing gear 7 are linked by the following relationship:

${{\tan\left( {{\delta{dir}} + {\beta\delta}} \right)} = {{\tan\left( {\beta T} \right)} + {\frac{d}{{V_{S}} \cdot {\cos({\beta T})}} \cdot r}}},$Where d is the distance along a longitudinal axis between the nose gearwheel 5 and the main landing gear 7.

The steering angle δdir may then be expressed as:

${\delta{dir}} = {{{atan}\left( {{\tan\left( {\beta T} \right)} + {\frac{d}{{V_{S}}{\cos\left( {\beta T} \right)}} \cdot r}} \right)} - {{\beta\delta}.}}$

Assuming that βδ and PT are small, the sideslip angle β may be expressedapproximately as:

${{\delta{dir}} \approx {{{atan}\left( {{\beta T} + {\frac{d}{V_{S}} \cdot r}} \right)} - {{\beta\delta}.}}}\;$

The lower δdir_(min) and upper δdir_(max) bounds of the steering anglerange [δdir_(min); δdir_(max)] of the nose gear wheel 5 are thusdetermined according to the following expressions:

${\delta{dir}}_{\min} = {{{atan}\left( {{\frac{d}{V_{S}} \cdot r} - {\beta T}_{\max}} \right)} - {\beta\delta}_{\max}}$${\delta{dir}}_{\max} = {{{atan}\left( {{\frac{d}{V_{S}} \cdot r} + {\beta T}_{\max}} \right)} + {{\beta\delta}_{\max}.}}$

Preferably, the steering angle range [δdir_(min); δdir_(max)] of thenose gear wheel 5 is further determined such that, when the steeringangle δdir of the nose gear wheel 5 is within said steering angle range,the sideslip angle βT of the left 7 a and right 7 b main landing gearsis lower, in absolute value, than the maximum sideslip angle δTmax.

The regulating assembly 60 is configured to determine an activationthreshold of the differential braking assembly 27′.

This activation threshold corresponds to a threshold value of thelateral trajectory parameter, in particular a curve radius thresholdvalue ρ_(seuil) or a yaw speed threshold value r_(seuil).

This activation threshold in particular corresponds to a threshold valueof a lateral trajectory parameter beyond which the differential brakingassembly 27′ is activated.

For example, this threshold value corresponds to a curve radiusthreshold value ρ_(seuil) below which the differential braking assembly27′ is activated, or a yaw speed threshold value r_(seuil) above whichthe differential braking assembly 27′ is activated.

Hereinafter, “activation threshold” will refer to this threshold value,and it will be considered that a lowering of this threshold correspondsto a relaxation of the criteria necessary for activation of thedifferential braking assembly 27′. A lowering of the threshold thereforefor example corresponds to an increase of the curve radius thresholdvalue ρ_(seuil) or to a decrease of the yaw speed threshold valuer_(seuil).

The regulating module 60 is preferably configured to determine theactivation threshold based on parameters relative to the movement of theaircraft on the ground, in particular:

-   -   information relative to the current speed of the aircraft 1, in        particular the modulus |V_(S)| of the current ground speed        vector of the aircraft, and/or    -   environmental parameters, in particular the estimated or        presumed current runway state (dry, wet or icy runway), and/or    -   operating parameters of the aircraft 1, in particular an        operating state of the nose gear wheel 5 and the temperature of        the braking devices 27 a, 27 b.

The regulating module 60 is able to receive said parameters from thedetermining assembly 35.

In particular, the regulating module 60 is configured to determine theactivation threshold based on current speed information of the aircraft.

The regulating module 60 is also configured to determine the activationthreshold based on the temperature of the braking devices 27 a, 27 b.Indeed, a high temperature leads to raising the activation threshold, toprevent an increase in the temperature of said braking devices 27 a, 27b as much as possible, which could cause a deterioration of the latter.

The regulating module 60 is further configured to determine theactivation threshold based on the operating state of the nose gear wheel5.

In particular, in case of failure or malfunction of the nose gear wheel5, the latter not being steerable, and freely rotating, the activationthreshold is lowered so as to make it possible to follow the desiredtrajectory despite the malfunction of the nose gear wheel 5.

Preferably, the regulating module 60 is also configured to determine theactivation threshold based on the steering angle range [δdir_(min);δdir_(max)] of the nose gear wheel 5.

In particular, the regulating module 60 is configured to receive saidsteering angle range [δdir_(min); δdir_(max)] from the limiting module58.

A reduction of this range [δdir_(min); δdir_(max)] generally leads tolowering the activation threshold.

In particular, the activation threshold is determined such that anyvalue of the considered trajectory parameter, below the threshold valueof said parameter (i.e., any curve radius greater than the curve radiusthreshold value ρ_(seuil), and/or any yaw speed below the yaw speedthreshold value r_(seuil)), may be reached by the aircraft without usingthe differential braking assembly 27′, and while keeping a steeringangle of the nose gear wheel 5 within the steering angle range[δdir_(min); δdir_(max)].

Thus, a decrease, in absolute value, of the lower δdir_(min) or upperδdir_(max) bound of the steering angle range leads to lowering thethreshold value of the trajectory parameter beyond which the activationof the differential braking assembly 27′ is necessary.

The module 62 for determining trajectories of the aircraft 1 isconfigured to determine, at each moment or sequentially, i.e., at aplurality of successive moments during the movement of the aircraft 1 onthe ground, a current trajectory of the aircraft, and at least one limittrajectory achievable by the aircraft 1 by actuating at least onelateral movement device.

Each of the current and limit trajectories is characterized by a lateralmovement direction and at least one lateral trajectory parameter, inparticular a curve radius and/or a yaw speed.

To that end, the determining module 62 is capable of receiving, from thedetermining assembly 35, parameters relative to the movement of theaircraft on the ground, in particular:

-   -   current speed information of the aircraft 1,    -   environmental parameters, in particular the estimated or        presumed to current runway state (dry, wet or icy runway),        —operating parameters of the aircraft 1, in particular an        operating state of the nose gear wheel 5,    -   a current setting of the lateral movement devices 13.

The determining module 62 is preferably also configured to receive, fromthe limiting module 58, at each moment or at a given frequency, thelower δdir_(min) and upper δdir_(max) bounds of the steering angle range[δdir_(min); δdir_(max)] of the nose gear wheel 5.

The determining module 62 is also configured to receive, from theregulating module 60, an activation threshold of the differentialbraking assembly 27 a, in particular a curve radius threshold valueρ_(seuil) or a yaw speed threshold value r_(seuil).

The current trajectory includes a series of waypoints predicted for atleast one element of the aircraft 1, under unchanged conditions of thelateral movement devices, but also when longitudinal movement devices 11are not actuated.

“Unchanged conditions of the lateral movement devices 13” means that thesettings of these devices remain unchanged relative to their currentsettings.

In other words, the current trajectory corresponds to the trajectorythat would or will be followed by the aircraft 1 on the ground if thelateral movement devices 13 a and 13 b keep their current settings, inparticular with a fixed steering angle of the nose gear wheel 5, a fixedorientation of the rudder 31 and a constant braking by the differentialbraking assembly 27′, and with unchanged outside conditions, inparticular wind.

The current trajectory is a trajectory of at least one element of theaircraft 1, such as the nose gear wheel 5, the nose of the aircraft, orthe end of a wing of the aircraft, or the tail of the aircraft.

Preferably, the determining module 62 is configured to determine acurrent trajectory of several elements of the aircraft 1, for examplechosen from among the nose gear wheel 5, the nose of the aircraft, theend of the left wing, the end of the right wing and the tail of theaircraft.

The determining module 62 is configured to determine the currenttrajectory of the aircraft, in particular characterized by the movementdirection, the curve radius and/or the associated yaw speed, from thecurrent speed information of the aircraft and the current settings ofthe lateral movement devices 13, and preferably the runway state and/oroperating parameters of the aircraft.

The determining module 62 is for example configured to determine thecurrent trajectory predicted over a preset distance or over a presettime interval, between the current determination moment and a timelimit, for example equal to 10 s.

The determining module 62 is further configured to determine, at eachmoment or sequentially, at least one limit trajectory achievable byactuating at least one lateral movement device 13.

Each limit trajectory includes, for each element of the consideredaircraft, a series of limit waypoints that may be reached by saidelement of the aircraft 1, by actuating at least one lateral movementdevice 13.

Each limit trajectory is for example a limit trajectory achievable byactuating:

-   -   only the nose gear wheel 5, or    -   only the rudder 31, or    -   only the differential braking assembly 27′, or    -   only the differential motor assembly 23′, or    -   at least two lateral movement devices 13.

Preferably, the determining module 62 is configured to determine atleast one first limit trajectory achievable by the aircraft 1 and atleast one second limit trajectory achievable by the aircraft 1.

“Limit trajectory” means that any point located beyond said limittrajectory, i.e., not between a longitudinal trajectory and said limittrajectory, cannot be reached by actuating the considered lateralmovement device(s) 13 within the authorized actuation limit(s) of saiddevices, in particular while remaining in the steering angle range[δdir_(min); δdir_(max)] of the nose gear wheel 5.

For example, the determining module 62 is configured to determine afirst limit trajectory achievable by actuating a first group of lateralmovement devices, and a second limit trajectory achievable by actuatinga second group of lateral movement devices, separate from the firstgroup. Each group comprises one or several lateral movement devices 13.

According to one preferred embodiment, the first limit trajectory is thelimit trajectory achievable by the aircraft 1 by using lateral movementdevices of the first assembly 13 a, the differential braking assembly27′ being inactive, i.e., not generating any lateral movement.Furthermore, the second trajectory is the limit trajectory achievable bythe aircraft 1 by using both the lateral movement devices of the firstset 13 a and the differential braking assembly 27′, the latter thereforebeing active.

The determining module 62 is thus configured to determine, at eachmoment or sequentially, at least one first limit trajectory achievableby actuating the devices of the first set 13 a of lateral movementdevices, the differential braking assembly 27′ being inactive.

Preferably, the determining module 62 is configured to determine twofirst limit trajectories, each corresponding to a respective lateralmovement direction.

The determining module 62 is thus able to determine a first limittrajectory oriented in a first direction, in particular to the left, anda first limit trajectory oriented in a second direction, in particularto the right, opposite the first direction.

Each first limit trajectory includes, for each element of the consideredaircraft, a series of first limit waypoints that may be reached by saidelement of the aircraft 1, by actuating at least one lateral movementdevice of the first set 13 a, preferably all of the devices of the firstset 13 a, the differential braking assembly 27′ being inactive.

“Limit trajectory” means that any point located beyond said limittrajectory, i.e., not between a longitudinal trajectory and said limittrajectory, cannot be reached when the differential braking assembly 27′is inactive.

In particular, if in the current state the differential braking assembly27′ is active, the first limit trajectory is a trajectory that would beobtained if the differential braking assembly 27′ was inactivated.

Each first limit trajectory is for example a circular trajectory, inparticular defined by a movement direction and by a first limit value ofa trajectory parameter.

This first limit value is for example a first minimum curve radiusρ_(min1) or a first maximum yaw speed r_(max1).

The determining module 62 is configured to determine the first limittrajectory, in particular the first limit value, from current speedinformation of the aircraft, the current settings of the lateralmovement devices 13, limit settings of the lateral movement devices ofthe first set 13 a, and preferably, the runway state and/or operatingparameters of the aircraft 1.

The limit settings of the lateral movement devices of the first set 13 ain particular include a limit orientation angle of the rudder 31.

This limit orientation angle for example has an absolute angle valuethat may not be exceeded by the rudder 31.

Preferably, this limit orientation angle has a preset value, lower thansaid absolute value.

The limit settings of the lateral movement devices of the first set 13 aalso include a limit orientation angle δdir_(lim) of the nose gear wheel5 in the considered lateral movement direction.

This limit steering angle is preferably equal to the lower δdir_(min) orupper δdir_(max) bound, depending on the considered movement direction,of the steering angle range [δdir_(min); δdir_(max)].

The first limit trajectory then corresponds to the trajectory it ispossible to achieve by modifying the settings of the nose gear wheel 5and optionally of the other lateral movement devices 13 a of the firstassembly, while remaining in the steering angle range [δdir_(min);δdir_(max)].

The first limit value of the trajectory parameter is then preferablyequal to the activation threshold of the differential braking assembly27′, as determined, then sent by the regulating module 60.

In particular, the first limit value of a trajectory parameter forexample includes a first minimum curve radius ρ_(min1) equal to thecurve radius threshold value ρ_(seuil).

Alternatively or additionally, the first limit value of a trajectoryparameter includes a first maximum yaw speed r_(max1) equal to the yawspeed threshold value r_(seuil).

Preferably, the determining module 62 is thus configured to determinethe first limit trajectory as a function of the considered lateralmovement direction, the activation threshold of the differential brakingassembly 27, and at least one piece of current speed information of theaircraft, in particular the modulus of the current ground speed vector.

The module 62 for determining trajectories of the aircraft 1 on theground is further configured to determine, at each moment or at aplurality of successive moments, at least one second limit trajectoryachievable by actuating both the devices of the first set 13 a oflateral movement devices and the differential braking assembly 27′.

Preferably, the determining module 62 is configured to determine twosecond limit trajectories, each corresponding to a respective lateralmovement direction.

The determining module 62 is thus able to determine a second limittrajectory oriented in a second direction, in particular to the left,and a first limit trajectory oriented in a second direction, inparticular to the right, opposite the first direction.

Each second limit trajectory includes, for each element of theconsidered aircraft, a series of second waypoints that may be reached bysaid element of the aircraft 1, by actuating at least one lateralmovement device of the first set 13 a, preferably all of the devices ofthe first set 13 a, the differential braking assembly 27′, the latterbeing active.

Each second limit trajectory is for example a circular trajectory,defined by a movement direction and by a second limit value of atrajectory parameter.

Said second limit value corresponds to a minimum or maximum value,depending on the considered parameter, of said parameter that it ispossible to achieve by using both the lateral movement devices of thefirst set 13 a and those of the second set 13 b.

This second limit value is for example a second minimum curve radiusρ_(min) or a second maximum yaw speed r_(max2).

The determining module 62 is configured to determine each second limittrajectory from:

-   -   the current speed information of the aircraft,    -   the current setting of the lateral movement devices 13,    -   limit settings of the lateral movement devices of the first set        13 a,    -   limit settings of the lateral movement devices of the second set        13 b,    -   and preferably, the runway state and/or operating parameters of        the aircraft 1.

As described above, the limit settings of the lateral movement devicesof the first set 13 a include a limit orientation angle δdir_(lim) ofthe nose gear wheel 5 in the considered lateral movement direction, saidlimit steering angle preferably being equal to the lower δdir_(lim) orupper δdir_(max) bound, depending on the considered movement direction,of the turning angle range [δdir_(min); δdir_(max)].

The second limit trajectory then corresponds to the trajectory it ispossible to achieve by modifying the settings of the nose gear wheel 5and other lateral movement devices 13, while remaining in the steeringangle range [δdir_(min); δdir_(max)].

The limit settings of the lateral movement devices of the second set 13b for example include a maximum braking force command differentialΔFmax.

Preferably, the operating parameters of the aircraft 1 including acurrent temperature of the braking devices 27 a, 27 b, the determiningmodule 62 is configured to determine the maximum braking force commanddifferential ΔFmax from said temperature.

In general, the maximum braking force command differential ΔFmax is adecreasing function of the temperature, at least when the temperature isabove a predetermined threshold temperature.

The second limit trajectory then corresponds to the trajectory that itis possible to achieve by actuating the differential braking assembly27′ and the other lateral movement devices 13, without risk of damagingthe braking devices.

The command assembly 50 is configured to acquire a lateral trajectoryorder, in particular an instruction lateral trajectory, entered by apilot.

Alternatively, the command assembly 50 is configured to acquire alateral trajectory order generated by an automatic pilot.

In the illustrated example, the command assembly 50 thus includes amanual command device 72, able to be actuated by the pilot to enter thelateral trajectory order.

Preferably, the manual command device 72 includes at least one commandmember movable by an operator between a first position and a secondposition, a movement of said command member between the first and secondposition being intended to generate a lateral trajectory order.

The lateral trajectory order acquired by the command assembly 50 thenincludes a signal representative of a position or movement value of saidcommand member.

Preferably, the manual command device 72 includes a rudder bar able tobe actuated by a pilot, from the cockpit.

The rudder bar includes a left pedal, intended to command a movement ofthe aircraft around the yaw axis in a first direction (in particular tothe left), and a right pedal, intended to command a movement of theaircraft around the yaw axis in a second direction (in particular theright) opposite the first direction.

According to one embodiment, the manual command device 72 furtherincludes a member for activating the differential braking assembly 27′.

This member for activating the differential braking assembly can beactuated by the pilot, from the cockpit, between an activated position,authorizing the implementation of the differential braking assembly togenerate a lateral movement of the aircraft 1, and a nonactivatedposition, prohibiting the implementation of the differential brakingassembly to generate such a lateral movement.

In the nonactivated position, the braking assembly 27 can be commandedsolely to exert, on the left main landing gear 7 a and the right mainlanding gear 7 b, a same force FTa=FTb opposing the movement of the left7 a and right 7 a main landing gears along the main rolling directionand thus to generate a longitudinal force opposing the longitudinalmovement of the aircraft.

The activating member is also configured to generate a signal foractivation or non-activation of the differential braking assembly 27′.

Preferably, the member for activating the differential braking assembly27′ is integrated into the rudder bar, as described in more detailbelow.

FIG. 6 thus shows a manual command device 72 according to one particularembodiment.

Said manual command device 72 includes a rudder bar 80 able to beactuated by a pilot, from the cockpit of the aircraft.

The rudder bar 80 includes a left pedal 82 a and a right pedal 82 b.

Each of the left 82 a and right 82 b pedals can be actuated by movementby the pilot in the cockpit.

In particular, an actuation of the left pedal 82 a by pressing on saidpedal 82 a is intended to command a movement of the aircraft around theyaw axis in a first direction, in particular to the left, and anactuation of the right pedal 82 b by pressing on said pedal 82 b isintended to command a movement of the aircraft around the yaw axis in asecond direction opposite the first direction, in particular to theright.

Each of the left 82 a and right 82 b pedals is movable between a neutralposition p_(n) and an end-of-travel position p_(f).

Preferably, the end-of-travel position is a stop position, past whichthe left 82 a and right 82 b pedals cannot be positioned.

The neutral position p_(n) of the left pedal 82 a, respectively of theright pedal 82 b, corresponds to an absence of lateral movement commandto the left, respectively to the right.

Preferably, a command play is provided around the neutral positionp_(n), such that a movement of the left and right pedals in closeproximity to the neutral position p_(n), is also associated with anabsence of lateral movement command to the left or to the right. Thisclose proximity is for example defined between the neutral position anda given position between the neutral position and the end-of-travelposition, for example a position located at Xj % of the total travelbetween the neutral position and the end-of-travel position. The valueXj % is for example between 1% and 5%, in particular about 3%.

The end-of-travel position p_(f) of the left pedal 82 a, respectively ofthe right pedal 82 b, corresponds to a maximum lateral movement commandto the left, respectively to the right.

In particular, the end-of-travel position p_(f) of the left pedal 82 a,respectively of the right pedal 82 b, corresponds to a lateral movementcommand according to the second limit value of a trajectory parameter asdetermined by the determining module 62, for example the second minimumcurve radius ρ_(min2) or the second maximum yaw speed r_(max2).

Each of the left pedals 82 a and 82 b is movable between a unique presettravel between the neutral position p_(n) and the end-of-travel positionp_(f).

Unique preset travel means that each point of the pedal is configured todescribe a unique journey when the pedal is moved from the neutralposition to the intermediate position, to the exclusion of any otherjourney.

Thus, each point of the pedal, and in general the pedal 82 a or 82 b, isfree to move along a single degree of freedom along the travel.

“Single degree of freedom” means that the position of the pedal in anyposition over the preset travel is described by a unique variable p_(c),without the movement of the pedal along the travel being limited to astraight translational movement.

The preset travel of each pedal is for example a movement chosen fromamong: a translational movement, in particular a straight or circulartranslational movement, a rotational movement, or a preset combinationof said movements.

For example, as illustrated in FIG. 6, each pedal 82 a, 82 b is mountedon a respective rudder bar 86 a, 86 b.

For example, each pedal 82 a, 82 b is mounted fixed on the rudder bar 86a, 86 b, and the rudder bar 86 a, 86 b is mounted rotatably around arotation axis A, which is a vertical axis in the illustrated example.

Alternatively, this rotation axis is a lateral axis or a longitudinalaxis.

Alternatively, each pedal 82 a, 82 b is mounted movably relative to therudder bar 86 a, 86 b, the movement of each pedal 82 a, 82 b withrespect to the rudder bar 86 a, 86 b being coupled with the rotation ofthe rudder bar 86 a, 86 b such that a movement of the pedal 82 a, 82 bdrives a rotational movement of the rudder bar 86 a, 86 b around itsrotation axis.

In one preferred embodiment, each of the left 82 a and right 82 b pedalsis further movable between a rear position p_(a) and the neutralposition p_(n), the neutral position p_(n) being between the rearposition p_(a) and the end-of-travel position, in particular midwaybetween the rear position p_(a) and the end-of-travel position p_(f).

In this embodiment, the rudder bar 82 includes a mechanism for couplingthe movement of the left 82 a and right 82 b pedals.

This coupling mechanism is configured, when the left 82 a or right 82 bpedal is moved toward the end-of-travel position p_(f), to move theright 82 b or left 82 a pedal, respectively, toward the rear positionp_(a).

For example, this coupling mechanism is configured, when the left 82 aor right 82 b pedal is moved toward the end-of-travel position p_(f), tocause a corresponding movement of the right 82 b or left 82 a pedal,respectively, toward the rear position p_(a).

In particular, the coupling mechanism is configured to cause a movementof the right pedal 82 b, respectively of the left pedal 82 a, to therear position p_(a), when the left pedal 82 a, respectively the rightpedal 82 b, is moved to the end-of-travel position p_(f). Each pedal 82a, 82 b is preferably movable along a unique preset travel between therear position p_(a) and the neutral position p_(n).

Moving a pedal “to” a position means moving the pedal toward thatposition, without it necessarily being necessary for this movement toresult in moving the pedal “up to” said position.

Thus, at a given moment, only one of the following configurations of theleft and right pedals is possible:

-   -   the left 82 a and right 82 b pedals are both located in their        respective neutral position p_(n), such a configuration being        associated with an absence of lateral movement command, or    -   the left pedal 82 a is positioned between the (strictly) neutral        position p_(n) and the end-of-travel position p_(f) and as a        result, the right pedal 82 b is positioned between the neutral        position p_(n) and the rear position p_(a), such a configuration        being associated with a lateral movement command to the left,    -   the right pedal 82 b is positioned between the (strictly)        neutral position p_(n) and the end-of-travel position p_(f) and        as a result, the left pedal 82 a is positioned between the        neutral position p_(n) and the rear position p_(a), such a        configuration being associated with a lateral movement command        to the right.

In the illustrated example, the coupling mechanism includes the rudderbars 86 a and 86 b, which are secured to one another, or made in onepiece.

The rudder bars 86 a, 86 b are arranged such that rotating one of thebars 86 a or 86 b around a rotation axis causes an identical rotation ofthe other bar 86 b, 86 a. Thus, moving one pedal toward theend-of-travel position p_(f) is able to cause a corresponding movementof the other pedal toward the rear position p_(a).

Preferably, each pedal 82 a, 82 b includes a return mechanism, intendedto exert a return force on the pedal 82 a, 82 b toward the neutralposition p_(n).

The return mechanism is configured to return the pedal 82 a, 82 b towardthe neutral position p_(n) when no force is exerted by the pilot on thepedal 82 a, 82 b.

The movement of the left 82 a or right 82 b pedal is intended to commanda movement of the aircraft around the yaw axis by actuating one orseveral lateral movement devices of the first set 13 a, the differentialbraking assembly 27′ being inactive, or by actuating one or severallateral movement devices of the first set 13 a and the differentialbraking assembly 27′, based on the current position p_(c) of the left 82a or right 82 b pedal along the travel.

The activation of the differential braking assembly 27′ depends on thecurrent position of the left 82 a or right 82 b pedal, relative to anintermediate position corresponding to an activation position p_(act) ofthe differential braking assembly 27′.

In particular, a movement of the left 82 a or right 82 b pedal betweenthe neutral position p_(n) and the activation position p_(act) along thepreset travel is intended to command a movement of the aircraft 1 aroundthe yaw axis Z₁-Z₁ by actuating one or several lateral movement devicesof the first set 13 a, the differential braking assembly 27′ beinginactive.

Such actuation is for example intended to command a movement of theaircraft 1 around the yaw axis Z₁-Z₁ by actuating the nose gear wheel 5and/or the rudder 31.

Furthermore, a movement of the left 82 a or right 82 b pedal along thepreset travel from the activation position p_(act) to the end-of-travelposition p_(f) is intended to command a movement of the aircraft 1around the yaw axis Z₁-Z₁ by actuating one or several lateral movementdevices of the first set 13 a, as well as the differential brakingassembly 27′, the latter being active.

The rudder bar 80 for example includes an acquisition device 90,configured to determine the instantaneous or current positions p_(c) ofthe left pedal 82 a and the right pedal 82 b.

The acquisition device 90 for example includes a left sensor, capable ofdetermining the current position of the left pedal 82 a, and a rightsensor, capable of determining the current position of the right pedal82 b.

The acquisition device 90 is furthermore configured to send thesecurrent positions p_(c) to the control assembly 52. For example, theacquisition device 90 is able to send the control assembly 52 a signalrepresentative of the current position p_(c).

The current position p_(c) of the left 82 a or right 82 b pedal alongthe preset travel constitutes a given lateral trajectory order.

In particular, this current position p_(c) is representative of alateral trajectory instruction parameter, in particular an instructioncurve radius or an instruction yaw speed.

As described in more detail below, the control assembly 52 is configuredto determine, from said lateral trajectory order, a command orderincluding one or several instruction parameters representative of theinstruction lateral trajectory.

The position of the left 82 a or right 82 b pedal, below or above theactivation position, is furthermore associated with a nonactivation oractivation order, respectively, of the differential braking assembly27′.

Furthermore, the rudder bar 80 includes a haptic feedback generator 92,configured to generate a haptic profile on each of the pedals 82 a, 82b, so as to have the pilot actuating said pedals feel a thresholdcrossing corresponding to the crossing of the activation positionp_(act) by one of the pedals, toward the end-of-travel position p_(f).

The haptic feedback generator 92 is in particular configured to apply,to each of the left 82 a and right 82 b pedals:

-   -   a first haptic profile when the left 82 a, respectively right 82        b, pedal is moved from the neutral position p_(n), to the        activation position p_(act), and    -   a second haptic profile, distinct from the first haptic profile,        when the left 82 a, respectively right 82 b, pedal is moved from        the activation position p_(act) to the end-of-travel position        p_(f).

For example, the haptic feedback generator 92 is configured to apply, toeach pedal 82 a, 82 b, a force opposing the movement of the pedal 82 a,82 b from the neutral position p_(n) to the end-of-travel positionp_(f). The haptic feedback generator 92 is in particular configured toapply, to each pedal 82 a, 82 b, a variable force Fh(p), as a functionof the current position p_(c) of the pedal 82 a, 82 b along the travel.

In particular, the haptic feedback generator 92 is configured to apply,to the left 82 a, respectively right 82 b, pedal, a force according to afirst force profile when the left 82 a, respectively right 82 b, pedalis moved from the neutral position p_(n), to the activation positionp_(act), and according to a second force profile, distinct from thefirst force profile, when the left 82 a, respectively right 82 b, pedalis moved from the activation position p_(act) to the end-of-travelposition p_(f).

Preferably, the first derivative of the force opposing the actuation ofthe pedal from the differential braking activation position p_(act) tothe end-of-travel position p_(f) is strictly greater than the firstderivative of the force opposing the actuation of the pedal to theactivation position p_(act).

In other words, the force profile applied by the haptic feedbackgenerator 92 includes a notch at the activation position p_(act).

In the present case, first derivative of the force Fh(p) relative to theposition p at the activation point p_(act) refers to the firstderivative on the right.

In particular, the haptic feedback generator 92 is configured to apply aforce opposing the actuation of the pedal 82 a, 82 b past the activationposition p_(act) that is greater than any force exerted by the hapticfeedback generator 92 in order to oppose the actuation of the pedal 82a, 82 b between the neutral position and the activation position.

The application of such a force, generating a hard spot for the movementof the pedal 82 a, 82 b past the activation position, makes it possibleto have the pilot feel the activation position, and thus to notify thepilot that an additional movement of the pedal will result in activatingthe differential braking assembly 27′.

The rudder bar 80 thus makes it possible to minimize the pilot'sworkload, the movement of each pedal by a single degree of freedomallowing the command of the lateral movement devices of the first set 13a and the differential braking assembly 27′, while retaining theinformation relative to the activation or non-activation of thedifferential braking assembly 27′.

The first force profile, applied between the neutral position p_(n) andthe activation position p_(act), is for example such that the forceFh(p) is an increasing function, in particular linear, of the positionof the pedal 82 a, 82 b [sic] the neutral position and the activationposition p_(act). The first profile is preferably such that the firstderivative of the force Fh(p) relative to the position p is below amaximum value denoted dFh_(max1).

The second force profile, applied between the activation positionp_(act) and the end-of-travel position p_(f), for example includes afirst portion, applied between the activation position p_(act) and theend-of-travel position p_(f), or between the activation position p_(act)and a first intermediate position p_(i1). On this first portion, theforce Fh(p) is an increasing function of the position of the pedalbetween the activation position p_(act) and the end-of-travel positionp_(f).

The first derivative of the force Fh(p) relative to the position p atthe activation point p_(act) is greater than the maximum valuedF_(max1).

If applicable, the second force profile includes a second portion,applied between the first intermediate position p_(i1) and theend-of-travel position p_(f).

On this second portion, the force Fh(p) is for example a decreasingfunction, or a function decreasing up to a second intermediate positionp_(i2), then increasing up to the end-of-travel position p_(f).

As an example, FIG. 7 illustrates a force profile applied by a hapticfeedback generator 92, corresponding to the superposition of a firstforce profile and a second force profile.

The first force profile, applied from the neutral position p_(n) up tothe activation position p_(act), is such that the force Fh(p) is anincreasing linear function of the position, the derivative of the forceFh(p) being constant, therefore equal to the maximum value dFh_(max1).

The second force profile includes first and second portions. On thefirst portion, from the activation position p_(act) up to the firstintermediate position p_(i1), the force Fh(p) is an increasing functionof the position, the first derivative of the force Fh(p) at theactivation point p_(act) being greater than the maximum value dF_(max1).

On the second portion, from the first intermediate position p_(i1) up tothe end-of-travel position p_(f), the force Fh(p) is first decreasing upto a second intermediate position p_(i2), then increasing up to theend-of-travel position p_(f).

It should be noted that in FIG. 7, the value of the force Fh applied inthe neutral position p_(n), is not necessarily nil.

Furthermore, although the force applied between the rear position p_(a)and the neutral position p_(n) is not illustrated, a non-nil force ispreferably applied between the rear position p_(a) and the neutralposition p_(n), this force for example being constant.

Preferably, the first and second force profiles are variable profiles,in particular as a function of the activation threshold of thedifferential braking assembly 27′ as determined by the regulating module60.

Alternatively, the first and second force profiles are preset fixedprofiles.

According to one preferred embodiment, the activation position p_(act)is associated with a variable value of a lateral trajectory instructionparameter, in particular an instruction curve radius or a variableinstruction yaw speed.

In this embodiment, the activation position p_(act) is in particularassociated with the activation threshold of the differential brakingassembly 27′ as determined by the regulating module 60.

This activation threshold corresponds to a threshold value of thelateral trajectory parameter, in particular a curve radius thresholdvalue ρ_(seuil) or a yaw speed threshold value r_(seuil).

In this embodiment, the activation position p_(act) is for examplevariable along the travel.

Alternatively, the activation position p_(act) is located in a fixedposition along the travel. According to this alternative, each positionof the pedals 82 a, 82 b between the neutral position p₁, and theend-of-travel position p_(f) is associated with a variable lateraltrajectory instruction parameter, in particular a variable instructioncurve radius or a variable instruction yaw speed.

According to another embodiment, the activation position p_(act) isassociated with a fixed value of an instruction parameter, in particularan instruction curve radius or instruction yaw speed fixed value.According to this alternative, the activation position p_(act) islocated in a fixed position along the travel.

The haptic feedback generator 92 for example includes a force profilegenerator 94 and a force generator 96.

The force profile generator 94 is configured to determine the first andsecond force profiles needing to be applied by the force generator 96.

Preferably, the force profile generator 94 is configured to determinethe force profiles as a function of the activation threshold of thedifferential braking assembly 27′ as determined by the regulating module60.

In particular, from this activation threshold, the profile generator 94is able to determine the activation position p_(act) along the travel,and to determine the force profiles from said activation positionp_(act).

The force generator 96 is able to exert, on each pedal 82 a, 82 b, aforce opposing the movement of the pedal 82 a, 82 b from the neutralposition to the end-of-travel position.

In particular, the force generator 96 is able to exert, on each pedal 82a, 82 b, a force according to the force profile determined by theprofile generator 94.

Alternatively, the force generator 96 is able to exert, on each pedal 82a, 82 b, a force according to fixed force profiles.

The force generator 96 includes at least one actuator, for example aleft actuator 98 a, capable of exerting a force on the left pedal 82 a,and a right actuator 98 b, capable of exerting a force on the rightpedal 82 b.

The actuator 98 a, 98 b for example comprises a motor.

The force generator 96 preferably includes a sensor capable ofdetermining the instantaneous position of the pedal 82 a, 82 b.

The sensor is for example a sensor of the acquisition device 90.

The force generator 96 further includes a command unit 102, configuredto command the actuator 98 a, 98 b to apply a force according to theforce profiles determined by the profile generator 94.

The command unit 102 is thus configured to command the actuator 98 a, 98b to apply a force as a function of the current position of said pedalas determined by the sensor.

In particular, the command unit 102 includes a memory for storing forceprofiles determined by the profile generator 94.

The command unit 102 is configured to receive, from the sensor at eachmoment, the current position of the pedals 82 a, 82 b.

The command unit 102 is further configured to determine the forceassociated with said current position according to the force profiles,and to command the application of said force by the actuator 98 a, 98 b.

Preferably, the manual command device 72 includes two rudder bars 80. Inparticular, the cockpit of the aircraft 1 includes two piloting units,each comprising a rudder bar 80. Preferably, the manual command device72 further includes a device for coupling the movements of the pedals ofthe rudder bars, capable, when the left 82 a or right 82 b pedal of afirst rudder bar is moved by a pilot, of causing a correspondingmovement of the left 82 a or right 28 b [sic] pedal of the second rudderbar.

Such coupling makes it possible to simplify the coordination of theactions by the pilots.

The control assembly 52 of the lateral trajectory is configured tocontrol the lateral movement devices 13 such that the aircraft 1 followsthe instruction lateral trajectory.

In particular, the control assembly 52 is configured to receive thelateral trajectory order acquired by the command assembly 50.

The control assembly 52 is further configured to convert said lateraltrajectory order into a command order, including one or severalinstruction parameters representative of the instruction lateraltrajectory.

The control assembly 52 is also configured to determine, from theinstruction parameters, instruction orders to be applied to one orseveral of the lateral movement devices 13 so that the aircraft followsthe instruction lateral trajectory, and to send said instruction ordersto the lateral movement devices.

In particular, the control assembly 52 is configured to determine thecommand orders such that the steering angle of the nose gear wheel 5remains in the steering angle range of the nose gear wheel [δdir_(min);δdir_(max)], as determined by the limiting module 58.

The control assembly 52 is further configured, if the instructionsteering angle does not make it possible to follow the instructionlateral trajectory, to determine instruction orders of one or severallateral movement devices 13 other than the nose gear wheel 5, inparticular the rudder 31, the braking assembly 27 of the main landinggear and/or the electric motors 23.

The control assembly 52 is further capable of receiving, from thedetermining assembly 35, parameters relative to the movement of theaircraft on the ground, in particular:

-   -   information relative to the current speed of the aircraft 1,    -   environmental parameters, in particular the estimated or        presumed current runway state (dry, wet or icy runway),    -   operating parameters of the aircraft 1, in particular an        operating state of the nose gear wheel 5,    -   a current setting of the lateral movement devices 13.

The assembly 52 for controlling the trajectory includes a command module120 and a control module 130.

The command module 120 is configured to receive the lateral trajectoryorder, and to convert said lateral trajectory order into a commandorder, including one or several instruction parameters representative ofthe instruction lateral trajectory.

Said instruction parameter(s) are in particular representative of thedirection of the lateral trajectory and the commanded curve radiusand/or yaw speed.

Said instruction parameters for example include an instruction curveradius ρ_(cons) and/or an instruction yaw speed r_(cons), associatedwith an instruction movement direction around the yaw axis.

These instruction parameters for example also include an activation ornon-activation order for the differential braking assembly 27′.

In particular, the command module 120 is configured to receive, from thecommand device 72, a signal representative of a current position or amovement of the command member.

For example, the command device 72 including a rudder bar 80 accordingto the embodiment described above, the command module 120 is configuredto receive, from the command device 72, in particular from theacquisition device 90, the current positions p_(c) of the left pedal 82a and the right pedal 82 b.

Preferably, the command module 120 is configured to receive, from theforce profile generator 94, in particular from the force profilegenerator 94, the current activation position p_(act).

The command module 120 is configured to determine the instructionparameters as a function of the lateral trajectory order, informationrelative to the current ground speed of the aircraft, in particular themodulus |V_(S)| of the ground speed vector, and the runway state.

Preferably, the command module 120 is also configured to determine theactivation or non-activation order of the differential braking assembly27′.

In particular, the command module 120 is configured to determine saidactivation or non-activation order from the activation or non-activationsignal sent by the activation member, and/or as a function of thelateral trajectory order.

According to one embodiment, the manual command device including arudder bar 80 as described above, the command module 120 is configuredto determine the activation or non-activation order from a comparisonbetween the current position p_(c) of the left 82 a and/or right 82 bpedal and the activation position p_(act).

The command module 120 is thus configured to:

-   -   generate an activation order of the differential braking        assembly 27′ if the current position p_(c) of the left pedal 82        a or the right pedal 82 b is past the activation position        p_(act), i.e., between the activation position p_(act) and the        end-of-travel position p_(f),    -   generate a non-activation order of the differential braking        assembly 27′ if neither of the current positions p_(c) of the        left 82 a and right 82 b pedals is past the activation position        p_(act).

Alternatively, the command module 120 is configured to determine saidactivation or non-activation order as a function of the determinedinstruction trajectory parameter(s).

In particular, the command module 120 is configured to determine theactivation or non-activation order from a comparison between theinstruction parameter(s) and the corresponding activation threshold(s),as determined, then sent to the regulating module 60.

The command module 120 is thus configured to:

-   -   generate an activation order of the differential braking        assembly 27′ if the instruction parameter exceeds the threshold        value of said parameter, in particular if the instruction curve        radius ρ_(cons) is below the curve radius threshold value        ρ_(seuil) and/or if the instruction yaw speed r_(cons) is above        the yaw speed threshold value r_(seuil),    -   generate a non-activation order of the differential braking        assembly 27′ if the instruction parameter does not exceed the        threshold value of said parameter, in particular if the        instruction curve radius ρ_(cons) is above the curve radius        threshold value ρ_(seuil) and if the instruction yaw speed        r_(cons) is below the yaw speed threshold value r_(seuil).

The command module 120 is able to send the control module 130 thetrajectory instruction parameter(s).

The control module 130 is configured to determine, from the lateraltrajectory order, in particular instruction parameters, instructionorders to be applied to one or several of the lateral movement devices13 so that the aircraft follows the instruction lateral trajectory.

The control module 130 is further configured to send these instructionorders to the lateral movement devices 13.

The control module 130 is in particular to determine an instructionsteering angle δdir_(cons), within the steering angle range [δdir_(min);δdir_(max)], the instruction steering angle δdir_(cons) being determinedsuch that, when it is applied to the nose gear wheel 5, the aircraft 1follows or tends toward the instruction lateral trajectory.

In other words, the instruction steering angle δdir_(cons) is determinedso as to create, when it is applied to the nose gear wheel 5, aneffective trajectory of the aircraft including a lateral movement of theaircraft 1 along the given direction and such that the curve radius ofsaid effective trajectory is greater than or equal to the instructioncurve radius.

To that end, the control module 130 is preferably configured todetermine, as a function of the lateral trajectory command order, aninitial steering angle δdir_(ini) of the nose gear wheel.

Said initial steering angle δdir_(ini) is for example determined so asto create, if it was applied to the nose gear wheel 5, a lateralmovement of the aircraft along the instruction lateral trajectory.

The control module 130 is furthermore configured to compare the initialsteering angle δdir_(ini) to the steering angle range [δdir_(min);δdir_(max)], and to apply a correction to the initial steering angleδdir_(ini) if it is not within the steering angle range, to determinethe instruction steering angle δdir_(cons).

When the initial steering angle δdir_(ini) is not within the steeringangle range, the instruction steering angle δdir_(cons) is for exampleequal to the lower or upper bound, respectively, of the steering anglerange [δdir_(min); δdir_(max)].

The control module 130 is furthermore configured to send a steeringinstruction to the nose gear wheel 5, in particular to the orientationdevice 9 of the nose gear wheel 5, in order to orient the nose gearwheel 5 according to the instruction steering angle δdir_(cons).

The control module 130 is further configured to determine, if theinstruction steering angle δdir_(cons) does not make it possible tofollow the instruction lateral trajectory, instruction orders of one orseveral lateral movement devices 13 other than the nose gear wheel 5, inparticular the rudder 31, the braking assembly 27 of the main landinggear, the set of electric motors 23 and/or the motors 19.

In particular, the control module 130 is configured to determine aninstruction orientation δn_(cons) of the rudder 31 and/or anasymmetrical braking instruction ΔF_(cons) of the differential brakingassembly 27′, and optionally an operating instruction of the electricmotors 23 a, 23 b and/or of the motors 19, used in differential mode.

Said instruction orientation on δn_(cons), asymmetrical brakinginstruction ΔF_(cons) and/or operating instruction of the motors 23 a,23 b and 19 are determined so as to create, when they are applied to therudder 31, the differential braking assembly 27′, the electric motors 23a, 23 b and the motors 19, respectively, the steering angle of the nosegear wheel being equal to the instruction steering angle δdir_(cons), alateral movement of the aircraft along the instruction lateraltrajectory.

For example, the instruction orientation δn_(cons) of the rudder 31, theasymmetrical braking instruction ΔF_(cons) and the operating instructionof the motors are determined so as to offset the difference between aninitial steering angle that would have been necessary to follow theinstruction lateral trajectory, and the instruction steering angle, whenthe latter does not make it possible to follow this trajectory.

The control module 130 is thus preferably configured to determine theinstruction orientation δn_(cons) and/or the asymmetrical brakingorientation ΔF_(cons) from the difference between the initial steeringangle δdir_(ini) and the instruction steering angle δdir_(cons).

The control module 130 is furthermore configured to send and orientationinstruction to the rudder 31, in particular to the orientation device 31of the rudder, in order to orient the rudder 31 according to theinstruction orientation δn_(cons).

If applicable, the control module 130 is also configured to send anasymmetrical braking instruction to the differential braking assembly27′, in particular to the control device 29 for the differential brakingassembly, in order to apply the asymmetrical braking instructionΔF_(cons) to the differential braking assembly 27′.

Preferably, the control module 130 is further configured to send the set23 of electric motors, in particular the control device 25 of theelectric motors, an operating instruction in order to apply thedetermined operating instruction to the electric motors 23 a, 23 b.

Preferably, when the command order includes an activation order for thedifferential braking assembly 27′, the control module 130 is configuredto determine the instruction orientation δn_(cons) of the rudder 31 andthe asymmetrical braking instruction ΔF_(cons) of the differentialbraking assembly 27′, and to send the orientation instruction to therudder 31 and the asymmetrical braking instruction to the differentialbraking assembly 27′.

The instruction orientation δn_(cons) and the asymmetrical brakinginstruction ΔF_(cons) are then determined so as to create, when they areapplied to the rudder 31 and to the differential braking assembly 27′,respectively, the steering angle of the nose gear wheel 5 being equal tothe instruction steering angle, a lateral movement of the aircraft alongthe instruction lateral trajectory.

Conversely, when the command order includes a non-activation order forthe differential braking assembly 27′, the control module 130 isconfigured to determine the instruction orientation of the rudder 31, tothe exclusion of the asymmetrical braking instruction of thedifferential braking assembly 27′, and to send the orientationinstruction to the rudder 31, without sending the asymmetrical brakinginstruction to the differential braking assembly 27′.

Preferably, the instruction orientation is then determined so as tocreate, when it is applied to the rudder 31, the steering angle of thenose gear wheel 5 being equal to the instruction steering angle and thedifferential braking assembly 27′ being inactive, a lateral movement ofthe aircraft along the instruction lateral trajectory.

Preferably, the control module 130 is further configured to determinethe instruction orientation of the rudder 31 based on informationrelative to the current ground speed of the aircraft.

Indeed, under certain conditions, in particular when the aircraft 1 isrolling at a low speed, the orientation of the rudder has little effecton the lateral trajectory of the aircraft.

In such a case, the control module 130 is for example configured todetermine the asymmetrical braking instruction ΔF_(cons) of thedifferential braking assembly 37′, to the exclusion of the instructionorientation of the rudder 31, and to send the asymmetrical brakinginstruction to the differential braking assembly 27′.

The asymmetrical braking instruction ΔF_(cons) is then preferablydetermined so as to create, when it is applied to the differentialbraking assembly 27′, the steering angle of the nose gear wheel 5 beingequal to the instruction steering angle, a lateral movement of theaircraft along the instruction lateral trajectory.

Preferably, the control module 130 is also configured to determine thecommand orders as a function of an operating state of the nose gearwheel 5, as acquired by the determining assembly 35.

In particular, in case of malfunction of the system for orienting thenose gear wheel 5, the nose gear wheel 5 may be non-steerable, whileremaining freely rotating.

In such a case, the control module 130 is configured to determine aninstruction orientation of the rudder 31 and/or an asymmetrical brakinginstruction of the differential braking assembly 27′, and optionally anoperating instruction of the electric motors 23 a, 23 b, and/or of themotors 19, used in differential mode. Said instructions are determinedso as to create, when they are applied to the rudder 31, thedifferential braking assembly 27′, the electric motors 23 a, 23 b and/orthe motors 19, respectively, a lateral movement of the aircraft alongthe instruction lateral trajectory.

According to one embodiment, the manual command device including arudder bar 80 as described above, the control module 130 is configured,selectively, to:

-   -   if none of the current positions p_(c) of the left and right        pedals are between the activation position p_(act) and the        end-of-travel position p_(f), send at least one input        instruction to the lateral movement devices of the first set 13        a, to the exclusion of the differential braking assembly 27′,        said input instruction being configured to create, when it is        applied to the lateral movement devices of the first set 13 a,        the differential braking assembly 27′ being inactive, a lateral        movement of the aircraft 1 according to or tending toward the        instruction lateral trajectory,    -   if the current position p_(c) of the left or right pedal is        between the activation position p_(act) and the end-of-travel        position p_(f), send input instructions to the lateral movement        devices of the first set 13 a and the differential braking        assembly 27′, said input instructions being configured to        create, when they are applied to the lateral movement devices of        the first set 13 a and the differential braking assembly 27′, a        lateral movement of the aircraft 1 according to or tending        toward the instruction lateral trajectory.

FIG. 8 illustrates a control module 130 according to one particularembodiment of the invention.

In this embodiment, the control module 130 includes a sub-module 132 fordetermining the initial steering angle δdir_(ini).

The sub-module 132 is configured to determine the initial steering angleδdir_(ini) of the nose gear wheel 5 as a function of the lateraltrajectory command order sent by the command module 120, in particularan instruction curve radius ρ_(cons) and/or an instruction yaw speedr_(cons), associated with an instruction movement direction around theyaw axis.

Preferably, the sub-module 132 is configured to determine the initialsteering angle δdir_(ini) further as a function of at least one piece ofinformation relative to the current speed of the aircraft, in particularas a function of the modulus |V_(S)| of the current ground speed and thecurrent yaw speed r.

The control module 130 also includes a sub-module 134 for determiningthe instruction steering angle δdir_(cons).

The sub-module 134 is configured to receive, from the limiting module58, the steering angle range [δdir_(min); δdir_(max)] of the nose gearwheel 5.

The sub-module 134 is further configured to receive, from the sub-module132, the initial steering angle δdir_(ini).

The sub-module 134 is configured to compare the initial steering angleδdir_(ini) to the steering angle range [δdir_(min); δdir_(max)], and toapply a correction to the initial steering angle δdir_(ini) if it is notwithin the steering angle range, to determine the instruction steeringangle δdir_(cons).

When the initial steering angle δdir_(ini) is not within the steeringangle range, the instruction steering angle δdir_(cons) is for exampleequal to the upper or lower bound, respectively, of the steering anglerange [δdir_(min); δdir_(max)].

The control module 130 further includes a sub-module 136 fordistributing additional instruction orders.

The distributing sub-module 136 is configured to receive, from thesub-module 132, the initial steering angle δdir_(ini).

The distributing sub-module 136 is also configured to receive, from thesub-module 134, the instruction steering angle δdir_(cons).

The distributing sub-module 136 is further configured to receive, fromthe determining assembly 35, information relative to the movement of theaircraft 1, in particular:

-   -   at least one piece of current speed information, in particular        the modulus |V_(S)| the current speed vector of the aircraft 1;    -   operating parameters of the aircraft 1, in particular an        operating state E_(dir) of the nose gear wheel 5.

The distributing sub-module 136 is also configured to receive, from thecommand module 120, an activation or non-activation order, denotedAct_(diff) in FIG. 8, for the differential braking assembly 27′.

The distributing sub-module 136 is configured to compare the instructionsteering angle δdir_(cons) to the initial steering angle δdir_(ini).

If the instruction steering angle δdir_(cons) is smaller, in absolutevalue, than the initial steering angle δdir_(ini), the sub-module 136 isconfigured to determine instruction orders of one or several lateralmovement devices 13 other than the nose gear wheel 5 such that, whenthese instruction orders are applied, the steering angle of the wheel 5being equal to the instruction steering angle δdor_(cons), the aircraft1 follows a trajectory according to the instruction lateral trajectory.

The distributing sub-module 136 is configured to determine theinstruction orientation δn_(cons) and/or the asymmetrical brakingorientation from the difference between the initial steering angleδdir_(ini) and the instruction steering angle δdir_(cons) or anexperienced steering angle, when the nose gear wheel 5 is not steerable,if applicable.

In particular, the distributing sub-module 136 is configured todetermine the instruction orientation δn_(cons) of the rudder 31 as afunction of the difference between the initial steering angle δdir_(ini)and the instruction steering angle δdir_(cons), and as a function of apiece of current speed information of the aircraft, in particular themodulus |V_(S)| of the current speed vector.

Indeed, the effect of the orientation of the rudder on the lateraltrajectory is greater when the modulus |V_(S)| of the current speedvector is high.

In this embodiment, the orientation of the rudder 31 is intended tocompensate, at least partially, the difference between the initialsteering angle δdir_(ini) and the instruction steering angleδdir_(cons).

The distributing sub-module 136 is furthermore configured to send andorientation instruction to the rudder 31, in particular to theorientation device 31 of the rudder, in order to orient the rudder 31according to the instruction orientation δn_(cons).

The distributing sub-module 136 is also configured to determine theasymmetrical braking instruction ΔF_(cons) as a function of:

-   -   an activation or non-activation order of the differential        braking assembly 27′,    -   the difference between the initial steering angle δdir_(ini) and        the instruction steering angle δdir_(cons),    -   a piece of current speed information of the aircraft, in        particular the modulus |V_(S)| of the current speed vector, and    -   an operating state of the device for orienting the nose gear        wheel 5.

In particular, if the order received from the command module 120 by thedistributing sub-module 136 is a non-activation order of thedifferential braking assembly 27′, the sub-module 136 is configured togenerate a non-activation instruction intended for the differentialbraking assembly 27′. This non-activation instruction is intended toprovide a nil force differential between the left 27 a and right 27 bbraking devices.

The distributing sub-module 136 is configured to send saidnon-activation instruction to the differential braking assembly 27′.

If the order received from the command module 120 by the distributingsub-module 136 is an activation order of the differential brakingassembly 27′, and if there is no malfunction of the device for orientingthe nose gear wheel 5, the sub-module 136 is configured to determine theasymmetrical braking instruction ΔF_(cons) as a function of thedifference between the initial steering angle δdir_(ini) and theinstruction steering angle δdir_(cons), current speed information of theaircraft, and preferably the instruction orientation δn_(cons).

The distributing sub-module 136 is also configured to send anasymmetrical braking instruction to the differential braking assembly27′, in particular to the control device 29 of the differential brakingassembly, in order to apply the asymmetrical braking instructionΔF_(cons) to the differential braking assembly 27′.

Furthermore, in case of malfunction of the system for orienting the nosegear wheel 5, the nose gear wheel 5 being non-steerable but free topivot, the sub-module 136 is configured to determine instruction ordersof one or several lateral movement devices 13 other than the nose gearwheel 5 such that, when these instruction orders are applied, theaircraft 1 follows a trajectory according to the instruction lateraltrajectory.

Thus, the distributing sub-module 136 is configured to determine aninstruction orientation δn_(cons) of the rudder 31 and/or anasymmetrical braking instruction of the differential braking assembly27′, and optionally an operating instruction of the electric motors 23a, 23 b, used in differential mode.

In particular, the distributing sub-module 136 is configured todetermine an instruction orientation δn_(cons) of the rudder 31 as afunction of the trajectory instruction parameter(s) or the initialsteering angle δdir_(ini), and a piece of current speed information ofthe aircraft, in particular the modulus |V_(S)| of the current speedvector.

Furthermore, if the order received from the command module 120 by thedistributing sub-module 136 is an activation order of the differentialbraking assembly 27′, and in case of malfunction of the device fororienting the nose gear wheel 5, the sub-module 136 is configured todetermine the asymmetrical braking instruction ΔF_(cons) as a functionof the trajectory instruction parameter(s) or the initial steering angleδdir_(ini), current speed information of the aircraft, and preferably,the instruction orientation δn_(cons).

The display assembly 54 includes a viewer 140 and a display generatingmodule 142 on the viewer.

The viewer 140 is for example at least partially transparent, such as asemitransparent screen intended to be placed in front of a windshield ofthe cockpit, a system for projecting images on the windshield of thecockpit, a semitransparent sunshade, a helmet visor, or asemitransparent glass close to the eye.

Alternatively, the viewer is a head down monitor integrated into thedashboard of the cockpit of the aircraft 1.

The generating module 142 includes means for processing graphicinformation, for example a graphics processor and an associated graphicsmemory. The graphics processor is suitable for processing graphicinformation stored in the graphics memory and displaying thatinformation or of a depiction thereof on the viewer 140.

The generating module 142 is configured to display a view of at least aportion of the runway on which the aircraft 1 is rolling on the viewer140.

This view of the runway portion is for example an egocentric view of therunway portion, i.e., seen from a viewpoint corresponding to the currentposition of the aircraft 1, for example a viewpoint located in thecockpit of the aircraft 1.

Alternatively, this view is an exocentric depiction of the runwayportion, i.e., seen from a virtual camera located at a point other thanthe current position of the aircraft. In particular, an exocentric imagecan correspond to an image that would be seen by a virtual camerasituated outside the aircraft and viewing the aircraft seen from behind,above and/or from the side.

The runway portion is for example representative of the terrain locatedin front of the aircraft, near a wing of the aircraft, or around theaircraft.

This view of the runway portion is for example an actual view of therunway portion. Such an actual view can be egocentric or exocentric.

For example, the display assembly 54 includes a camera on board theaircraft, in particular in the nose or at the end of a wing of theaircraft.

Based on data from the images acquired by the camera, the generatingmodule 142 is able to display, on the viewer 140, an actual image of theenvironment present in front of or around the aircraft. This actual viewis then an egocentric depiction.

Alternatively, the display assembly 54 is configured to receive, from acamera outside the aircraft, for example a camera located on the runway,images representative of the runway portion, and to generate the displayof an actual image of the environment present in front of or around theaircraft from images received from said camera. This actual view is thengenerally exocentric.

Alternatively, the viewer 140 being a head-up display, this actual viewis for example seen through the windshield of the cockpit.

According to another example, the view of the runway portion is asynthetic depiction of the runway portion.

In particular, the generating module 142 is configured to generate thissynthetic depiction from a current position of the aircraft 1 on therunway and a topographical database stored in a memory.

The generating module 142 is for example configured to receive thecurrent position of the aircraft from the determining assembly 35.

The synthetic depiction is for example egocentric. Alternatively, it isexocentric. Such an exocentric depiction for example corresponds to animage that would be seen by a virtual camera situated outside theaircraft and viewing the aircraft.

The generating module 142 is further configured to display a set ofcurves on the viewer 140 including:

-   -   a current trajectory curve, representative of the current        trajectory of the aircraft,    -   at least one limit curve representative of a limit trajectory of        the aircraft 1.

The current trajectory includes a series of waypoints predicted for atleast one element of the aircraft 1, under unchanged conditions of thelateral movement devices of the first and second sets 13 a, 13 b, i.e.,in the absence of any modification of the settings of these devices.

Said element(s) are for example chosen from among the nose gear wheel 5,the nose of the aircraft, or the end of a wing of the aircraft, or thetail of the aircraft 1.

The limit trajectory includes a series of limit waypoints that may bereached by said element(s) of the aircraft 1, by actuating at least onelateral movement device 13.

Each limit trajectory is for example a limit trajectory achievable byactuating:

-   -   only the nose gear wheel 5, or    -   only the rudder 31, or    -   only the differential braking assembly 27′, or    -   only the differential motor assembly 23′, or    -   at least two lateral movement devices.

“Limit trajectory” means that any point located beyond said limittrajectory, i.e., not between a longitudinal trajectory and said limittrajectory, cannot be reached by actuating the considered lateralmovement device(s) 13.

The generating module 142 is preferably configured to acquire saidtrajectories from the trajectory determining module 62.

Thus, the limit curve is preferably representative of the limittrajectory as determined by the determining module 62.

The generating module 142 is configured to display said curves on theviewer 140 superimposed on the view of the runway.

Thus, the display of said curves allows the pilot to view, directly onthe viewer, the current trajectory and the limit trajectory.

Preferably, the generating module 142 is configured to display at leastone first limit trajectory achievable by the aircraft 1 and at least onesecond limit trajectory achievable by the aircraft 1.

For example, the generating module 142 is configured to display at leastone first limit curve representative of a first limit trajectoryachievable by actuating a first group of lateral movement devices, and asecond limit curve representative of a second limit trajectoryachievable by actuating a second group of lateral movement devices,separate from the first group. Each group comprises one or severallateral movement devices 13.

The generating module 142 is thus configured to display a set of curveson the viewer 140 including:

-   -   a current trajectory curve, representative of the current        trajectory of the aircraft,    -   a first limit curve representative of a first limit trajectory        of the aircraft 1, and    -   a second limit curve representative of a second limit        trajectory.

The first and second limit curves are preferably representative of thefirst and second limit trajectories as determined by the determiningmodule 62.

Thus, the display of said curves allows the pilot to view, directly onthe viewer, the current trajectory, the first limit trajectory and thesecond limit trajectory.

Preferably, as described above, the first limit trajectory includes aseries of first limit waypoints that may be reached by the consideredelement(s) of the aircraft 1, by actuating at least one lateral movementdevice of the first set 13 a, the differential braking assembly 27′being inactive.

The second limit trajectory includes a series of second limit waypointsthat may be reached by said element(s) of the aircraft 1, by actuatingat least one lateral movement device of the first set 13 a and thedifferential braking assembly 27′, the latter being active.

The current trajectory curve is representative of the current trajectoryover a preset current trajectory display distance Dc.

Each limit curve is representative of the limit trajectory over a presetlimit trajectory display distance Dl.

For example, the first limit curve is representative of the first limittrajectory over a first preset limit trajectory display distance Dl1,and the second limit curve is representative of the second limittrajectory over a second preset limit trajectory display distance Dl2.

The current trajectory curve display distance Dc is for exampledifferent from the limit trajectory display distances Dl.

The display distances Dl1 and Dl2 of the first and second limittrajectories are for example identical.

Alternatively, the display distances Dl1 and Dl2 are different.

Preferably, the display distances Dc, Dl1 and Dl2 are variable.

Preferably, each display distance Dc, Dl1 and Dl2 is a function of thecurrent speed of the aircraft, in particular the modulus |V_(S)| of thecurrent ground speed vector of the aircraft.

FIG. 9 illustrates, as an example, the display distance Dc, Dl1 or Dl2(denoted D on the Y axis of FIG. 9), as a function of the modulus|V_(S)| of the current ground speed vector. In this example, eachdisplay distance Dc, Dl1 and Dl2 is an increasing function, inparticular linear, of the modulus |V_(S)| of the current ground speedvector when the modulus |V_(S)| is within a preset speed range [V1; V2].In this speed range, each current or limit curve is preferablyrepresentative of the current or limit trajectory over a constantduration, independently of the speed.

When the modulus |V_(S)| of the current ground speed vector is below thethreshold V1 or above the threshold V2, the display distance Dc, Dl1,Dl2 is constant, i.e., independent of the speed.

In particular, when the modulus |V_(S)| of the current ground speedvector is below the threshold V1, respectively above the threshold V2,the display distance Dc, Dl1, Dl2 is equal to a constant distance Dmin,respectively Dmax.

The display generating assembly 142 is configured to determine eachdisplay distance Dc, Dl1, Dl2 as a function of the modulus of thecurrent ground speed vector |V_(S)| of the aircraft 1.

Preferably, as illustrated in FIG. 9, the display generating assembly142 is configured to display, on the viewer 140, the current trajectorycurve, the first limit curve and/or the second limit curve when a speedof the aircraft 1 is between a preset minimum bound V_(min) and maximumbound V_(max), and to eliminate, from the viewer 140, the currenttrajectory curve, the first limit curve and/or the second limit curvewhen the speed of the aircraft 1 is below the minimum bound V_(min) orabove the maximum bound V_(max).

Eliminating the curves from the viewer 140 makes it possible to avoidoverloading the viewer with information that is not very useful undercertain circumstances, for example when the aircraft is rolling at avery low speed or high speed during a takeoff phase, the aircraft thengenerally having a longitudinal trajectory.

Preferably, the generating module 142 is configured to display, on theviewer 140:

-   -   a first left limit curve representative of a first left limit        trajectory including a yaw movement in the first direction (to        the left) and/or a first right limit curve, representative of a        first right limit trajectory including a yaw movement in the        second direction (to the right),    -   a second left limit curve representative of a second left limit        trajectory including a yaw movement in the first direction        and/or a second right limit curve, representative of a second        right limit trajectory including a yaw movement in the second        direction.

Preferably, the generating module 142 is configured to display,selectively on the viewer 140, the first and/or the second limit curvecorresponding to a trajectory oriented in the same direction as thecurrent trajectory of the aircraft 1, to the exclusion of the firstand/or second limit curve corresponding to a trajectory oriented in thedirection opposite the current direction of the trajectory.

“Direction” of a trajectory refers to the direction of the lateralmovement of the aircraft around the yaw axis along said trajectory(i.e., according to a positive or negative angle).

Thus, the generating module 142 is configured to display, selectively onthe viewer 140:

-   -   at least one of the first left limit curve and second left limit        curve if the current trajectory is oriented in the first        direction, or    -   at least one of the first right limit curve and second right        limit curve if the current trajectory is oriented in the second        direction.

It will be understood that the selective display of at least one of thefirst and second left limit curves means that the first and second rightlimit curves are not displayed.

Likewise, it will be understood that the selective display of at leastone of the first and second right limit curves means that the first andsecond left limit curves are not displayed.

Such a display makes it possible to avoid overloading the viewer 140with information that is not very useful to the pilot.

According to one preferred embodiment, the generating module 142 isconfigured to display, selectively on the viewer 140, at least one ofthe first and second left limit curves, if and only if the currenttrajectory is oriented in the first direction and one of the followingconditions is met:

the yaw angle λ of the aircraft 1 being increasing, the currenttrajectory is such that the yaw angle λ is greater than a left displaythreshold yaw angle λ_(a), or

the yaw angle of the aircraft 1 being decreasing, the current trajectoryis such that the yaw angle is greater than a left erasure threshold yawangle λ_(e) (smaller than the left display threshold yaw angle λ_(a)).

Likewise, the generating module 142 is configured to display,selectively on the viewer 140, at least one of the first and secondright limit curves, if and only if the current trajectory is oriented inthe second direction and one of the following conditions is met:

the yaw angle of the aircraft 1 being decreasing (therefore increasingin absolute value), the current trajectory is such that the yaw angle λis less than a right display threshold yaw angle λ_(a′), or

the yaw angle of the aircraft 1 being increasing (therefore decreasingin absolute value), the current trajectory is such that the yaw angle isless than a right erasure threshold yaw angle λ_(e′) (greater than theright display threshold yaw angle λ_(a′)).

Preferably, the left λ_(a) and right λ_(a′) display threshold yaw anglesare equal in absolute value, and the left λ_(e) and right λ_(e′) erasurethreshold yaw angles are equal in absolute value.

FIG. 10 thus shows a display profile according to one embodiment. Inthis figure, the values ‘1’ and ‘−1’ on the Y axis correspond to adisplay by the generating module 142 of the first and/or second left orright limit curves, respectively. The value ‘0’ corresponds to anabsence of display of the limit curves.

Such a display with hysteresis makes it possible to avoid a blinkingeffect by repeated displays and disappearances of the curves when theyaw angle of the aircraft is close to the display threshold yaw angle.

Furthermore, the current trajectory curve is preferably displayedaccording to a different graphic format from the graphic format of thefirst and second limit curves.

A graphic format is defined by a set of display parameters, inparticular a color, a line type (continuous, dotted, etc.) and/or a linethickness.

In particular, at least one of the display parameters of the graphicformat of the current trajectory curve differs from the correspondingparameter of the graphic format of the first limit curve.

Likewise, at least one of the display parameters of the graphic formatof the current trajectory curve differs from the corresponding parameterof the graphic format of the second limit curve.

Preferably, at least one of the display parameters of the graphic formatof the current trajectory curve differs from the corresponding parameterof the graphic format of the first limit curve and from thecorresponding parameter of the graphic format of the second limit curve.

Preferably, the display format of the first limit curve also differsfrom the display format of the second limit curve.

Such a display allows a more effective identification of thetrajectories, in particular a faster identification of the trajectorytypes associated with the displayed curves.

Preferably, textual indications are further displayed below the currenttrajectory curve, the first limit curve and/or the second limit curve.These textual indications are indicative of the associated type ofcurve, in particular current trajectory curve, first or second limitcurve, and allow an even faster identification of trajectory typesassociated with the displayed curves.

Preferably, the generating module 142 is configured to display, on theviewer 140, several curves representative of current trajectories ofseveral elements of the aircraft, several first limit curvesrepresentative of first limit trajectories of said elements, and severalsecond limit curves representative of second limit trajectories of saidelements.

For example, said elements are the ends of the two wings of the aircraft1.

In particular, the generating module 142 is configured to display thecurrent trajectory curves, each representative of the current trajectoryof one end of a respective wing.

These the current curves define a surface on the runway that will beswept by the aircraft if it follows the current trajectory.

The generating module 142 is also configured to display two first limitcurves, each representative of a first limit trajectory of one end of arespective wing, and two second limit curves, each representative of asecond limit trajectory of one end of a respective wing.

Such a depiction thus allows the pilot to view and avoid any obstaclesthat may be located on the runway, along the current trajectory or atargeted trajectory.

Preferably, in this embodiment, the generating module 142 is configuredto display only the first and/or the second limit curve of a wing ifsaid limit curves are oriented in the direction associated with the sideof the wing.

In particular, the generating module 142 is configured to display onlythe first and/or the second left limit curve of the left wing and thefirst and/or the second right limit curve of the right wing.

Preferably, the generating module 142 is configured to display only thefirst and/or the second limit curve of each wing corresponding to thelimit trajectories that are both:

-   -   oriented in the same direction as the current trajectory of the        wing, and    -   oriented in the direction associated with the side of the wing.

Thus, the generating module 142 is configured to display, selectively onthe viewer 140:

-   -   the first and/or the second left limit curve of the end of the        left wing if the current trajectory is oriented to the left, or    -   the first and/or the second right limit curve of the end of the        right wing if the current trajectory is oriented to the right.

FIGS. 11 to 16 show display examples on a viewer.

FIGS. 11 to 16 in particular illustrate a display on a head-up viewer.

In FIG. 11, the view 200 of the runway portion 3 located in the aircraft1 is an actual, egocentric view, as seen from the nose of the aircraft.

A current trajectory curve 202, representative of the current trajectoryof the aircraft 1, in particular the nose of the aircraft, issuperimposed on the view 200.

In this example, the current trajectory is a substantially longitudinaltrajectory.

Thus, also superimposed on the view 200 are:

-   -   a first left limit curve 204 a and a first right limit curve 204        b,    -   a second left limit curve 206 a and a second right limit curve        206 b.

In this example, the current trajectory curve 202, the first limitcurves 204 a, 204 b and the second limit curves 206 a, 206 b, aredisplayed in three different graphic formats.

In particular, the current trajectory curve 202 is displayed in the formof a continuous line, the first limit curves 204 a, 204 b are displayedin the form of a dotted line of a first type, and the second limitcurves 206 a, 206 b are displayed in the form of a dotted line of asecond type.

The display example of FIG. 12 differs from the display example of FIG.11 in that the current trajectory is not a longitudinal trajectory, buta trajectory including a movement of the aircraft around the yaw axis tothe right, at a low speed.

In this situation, the first and second left limit curves 204 a and 206a are therefore not displayed. Thus, only the first and second rightlimit curves 204 b and 206 b are displayed.

FIG. 13 illustrates a display example similar to FIG. 12, but at ahigher speed.

In this situation, the current trajectory includes a movement of theaircraft around the yaw axis to the right.

Nevertheless, due to the higher speed of the aircraft, the curve radiusis greater than in the situation of FIG. 12. The first and second leftlimit curves 204 a and 206 a are then displayed, as well as the firstand second right limit curves 204 b and 206 b.

FIGS. 14 to 16 illustrate one embodiment of a head-down viewer.

The embodiment illustrated in FIG. 14 differs from the embodimentillustrated in FIG. 12 in that the view 210 is a synthetic image 200 ofthe runway portion located in front of the aircraft.

Furthermore, the first and second right limit curves 204 b, 206 b aredisplayed in the same graphic format, in particular in the form of adotted line of a same type.

The embodiment illustrated in FIG. 15 differs from the embodimentillustrated in FIG. 14 in that the view 121 is synthetic image of therunway portion located in front of the aircraft.

Furthermore, in FIG. 15 and in FIG. 13, the current trajectory is not alongitudinal trajectory, but a trajectory including a movement of theaircraft around the yaw axis to the right, and the first and second leftlimit curves 204 a and 206 a, as well as the first and second rightlimit curves 204 b, 206 b, are displayed.

In the embodiment illustrated in FIG. 16, the view 214 displayed on theviewer is an exocentric depiction, seen from at least one actual cameralocated above the aircraft 1.

In this example, two current trajectory curves 202 a and 202 b, eachrepresentative of the current trajectory of one end of a respectivewing, are displayed.

The ends of said curves are connected to one another by two segments 202c, 202 d.

The two current trajectories 202 a and 202 b, as well as the segments202 c, 202 d, therefore define a surface on the runway that would beswept by the aircraft if it followed the current trajectory.

In the embodiment illustrated in FIG. 16, the current trajectoryincludes a movement of the aircraft around the yaw axis to the right.Thus, only the first and second right limit curves 204 b, 206 b of theright wing are displayed.

According to one embodiment, the control system 40 includes aninformation processing unit, for example formed by a processor and amemory associated with the processor. The modules for limiting 58,regulating 60, determining trajectories 62, command 120, control 130,and generating 142, and the sub-modules 132, 134 and 136 are then forexample each made in the form of software executable by the processorand stored in the memory.

Alternatively, the limiting 58, regulating 60, trajectory determining62, command 120, control 130, and generating 142 modules, and thesub-modules 132, 134 and 136 are each made in the form of a programmablelogic component, such as an FPGA (Field Programmable Gate Array), or inthe form of a dedicated integrated circuit, such as an ASIC (ApplicationSpecific Integrated Circuit).

FIG. 17 shows a block diagram of a method for controlling the lateraltrajectory of an aircraft rolling on the ground on a runway, accordingto a first aspect.

Said method is implemented in an aircraft 1 as described in reference toFIGS. 1 to 3, and preferably using a control system 40.

Said method includes a step 300 for determining a current trajectory ofthe aircraft 1 on the ground. Said current trajectory includes a seriesof waypoints predicted for at least one element of the aircraft 1, whenthe lateral movement devices of the first set 13 a and the differentialbraking assembly 27′ are not actuated.

The or each element are 1 is for example chosen from among the nose gearwheel 5, a nose of the aircraft, an end of a left wing of the aircraft,an end of a right wing of the aircraft and the tail of the aircraft 1.

The method further includes a step for determining 302 at least onelimit trajectory, including a series of limit waypoints that may bereached by the element of the aircraft 1 by actuating at least onelateral movement device 13.

In one preferred embodiment, the step 302 includes a phase 304 fordetermining at least one first limit trajectory, including a series offirst limit waypoints able to be reached by the element of the aircraft1 by actuating at least one lateral movement device of the first set 13a, the differential braking assembly 27′ being in the inactive state.

Preferably, the phase 304 includes determining two first limittrajectories, including a first left limit trajectory associated with ayaw movement in a first direction, and a first right limit trajectory,associated with a yaw movement in a second direction, opposite the firstdirection.

Preferably, each first limit trajectory is determined as a function of apreset activation threshold of the differential braking assembly 27′ andat least one piece of current speed information of the aircraft.

The activation threshold is for example determined as a function of atleast one parameter chosen from among the information relative to thecurrent speed of the aircraft 1, a current runway state, an operatingstate of the nose gear wheel 5 and a temperature of braking devices 27a, 27 b of the differential braking assembly 27′.

Said activation threshold is for example determined by a regulatingmodule 60 as described above.

Preferably, as described above, each first limit trajectory correspondsto a trajectory that it is possible to achieve by modifying the settingsof the nose gear wheel 5 and optionally of the other lateral movementdevices 13 a of the first assembly, while remaining in the steeringangle range.

This steering angle range is for example determined as a function ofinformation relative to the current speed of the aircraft and themaximum authorized sideslip angle βδ_(max), βT_(max), during a step 330described below.

The step 302 further preferably includes a phase 308 for determining atleast one second limit trajectory, including a series of second limitwaypoints able to be reached by the element of the aircraft 1 byactuating at least one lateral movement device of the first set 13 a andthe differential braking assembly 27′, the differential braking assembly27′ being active.

Preferably, the phase 308 includes determining two second limittrajectories, including a second left limit trajectory associated with ayaw movement in the first direction, and a second right limittrajectory, associated with a yaw movement in the second direction.

The determining steps 300 and 302 are for example carried out by atrajectory determining module 62 as described above.

The method also includes a step 310 for displaying, on a viewer, forexample the viewer 140:

-   -   a view of a runway portion 3 located near the aircraft 1;    -   a current trajectory curve representative of the current        trajectory; and    -   at least one limit curve representative of the limit trajectory,    -   said curves being superimposed on the view of the portion of the        runway.

Said display step 310 is for example carried out by the generatingmodule 142 described above.

The view of the runway portion is for example an egocentric view of therunway portion, seen from a viewpoint located in the cockpit of theaircraft, or an exocentric view of the runway portion, seen from aviewpoint located outside the aircraft.

The view of the runway portion is for example an actual view of therunway portion, or a synthetic depiction of the runway portion,generated from a current position of the aircraft 1 on the runway and atopographical database.

According to one preferred embodiment, the step 310 includes the displayon a viewer, for example the viewer 140, of:

-   -   the view of a runway portion 3 located near the aircraft 1;    -   at least a first limit curve representative of the first limit        trajectory, and    -   at least one second limit curve representative of the second        limit trajectory, said curves being superimposed on the view of        the portion of the runway.

Preferably, step 310 includes the display of a first left limit curverepresentative of the first left limit trajectory and/or a first rightlimit curve representative of the first right limit trajectory.

Furthermore, step 310 for example includes the display of a second leftlimit curve representative of the second left limit trajectory and/or asecond right limit curve representative of the second right limittrajectory.

Preferably, if the current trajectory is oriented in the firstdirection, step 310 includes the display of at least one of the firstand second left limit curves, the right limit curves not beingdisplayed.

On the contrary, if the current trajectory is oriented in the seconddirection, step 310 includes the display of at least one of the firstand second right limit curves, the left limit curves not beingdisplayed.

The current trajectory curve, the first limit curve(s) and/or the secondlimit curve(s) are representative of the current trajectory, the firstlimit trajectory and/or the second limit trajectory respectively overpreset distances, as described above.

FIG. 18 illustrates a control method according to a second aspect.

This method is for example carried out after steps 300 to 310 of themethod according to the first aspect, or concomitantly with said steps.

Said method includes a step 320 for generating an order commanding aninstruction lateral trajectory of the aircraft 1. This instructionlateral trajectory includes a lateral movement of the aircraft 1 in agiven direction. Said command order includes at least one instructionparameter representative of the instruction trajectory.

Said generating step 320 for example includes a sub-step 322 for theactuation by a pilot of the command device 72, for example the rudderbar 80 as described above, to generate a lateral trajectory order.

The generating step 320 further includes a sub-step 324 for generating,in particular by the command module 120, the command order from thelateral trajectory order.

Preferably, the command order includes an activation or non-activationorder of the differential brake 27′.

For example, the command device including the rudder bar 80, thesub-step for example includes generating an activation order of thedifferential braking assembly 27′ if the current position p_(c) of theleft pedal 82 a or the right pedal 82 b is between the activationposition p_(act) and the end-of-travel position p_(f), or generating anon-activation order of the differential braking assembly 27′ if thecurrent position p_(c) of the left pedal 82 a and the current positionof the right pedal 82 b are between the neutral position p_(n) and theactivation position p_(act).

The method further includes a step 330 for determining a steering anglerange [δdir_(min); δdir_(max)] of the nose gear wheel 5, outside which arisk of loss of adhesion of the nose gear wheel 5 is significantlyincreased.

This step 330 is for example carried out by the limiting module 58 asdescribed above.

This determining step 330 includes a sub-step 332 for evaluatinginformation relative to a current speed of the aircraft relative to theground and at least one maximum authorized sideslip angle βδ_(max),βT_(max) of the nose gear wheel 5 and/or main landing gear 7 a, 7 b ofthe aircraft 1.

The information relative to the current ground speed of the aircraft forexample includes the modulus of the current ground speed vector of theaircraft, and the current yaw speed of the aircraft.

The sub-step 332 preferably includes receiving or estimating a parameterrepresentative of an adhesion state of the runway (dry, wet or icyrunway, for example), and determining the maximum authorized sideslipangle βδ_(max), βT_(max) as a function of said parameter representativeof the adhesion state of the runway.

The maximum authorized sideslip angle βδ_(max), βT_(max) is for exampleevaluated from the database.

The determining step 330 further includes a sub-step 334 fordetermining, as a function of information relative to the current speedof the aircraft and the maximum authorized sideslip angle βδ_(max),βT_(max), the steering angle range [δdir_(min); δdir_(max)] of the nosegear wheel 5 such that, when a steering angle δdir of the nose gearwheel 5 is within said steering angle range [δdir_(min); δdir_(max)],the steering angle 136, 13T of the nose gear wheel 5 and/or the mainlanding gear 7 a, 7 b is less, in absolute value, than the maximumsteering angle βδ_(max), βT_(max).

The method further includes a step 340 for controlling the lateralmovement devices. The step 340 is for example carried out by the controlmodule 130 as described above.

Said step 340 includes a sub-step 342 for determining, as a function ofthe command order, an instruction steering angle δdir_(cons) of the nosegear wheel 5, within the steering angle range [δdir_(min); δdir_(max)].Said instruction steering angle δdir_(cons) is determined so as tocreate, when it is applied to the nose gear wheel 5, a lateral movementof the aircraft 1 according to or tending toward said instructionlateral trajectory.

The sub-step 342 for example includes a phase 344 for determining, basedon the command order, an initial steering angle δdir_(ini) of the nosegear wheel 5, said initial steering angle δdir_(ini) being determined soas to create, if it is applied to the nose gear wheel 5, a lateralmovement of the aircraft 1 according to or tending toward saidinstruction lateral trajectory.

The sub-step 342 then further includes a phase 346 for applying acorrection to the initial steering angle if said initial steering angleis not within the steering angle range [δdir_(min); δdir_(max)], todetermine the instruction steering angle δdir_(cons).

Step 340 further includes a sub-step 348 for sending a steeringinstruction to the nose gear wheel 5 in order to orient the nose gearwheel 5 according to the instruction steering angle δdir_(cons).

According to one embodiment, step 340 further includes a sub-step 350for determining an instruction orientation δn_(cons) of the rudder 31and/or an asymmetrical braking instruction ΔF_(cons) of the differentialbraking assembly 27′.

The instruction orientation δn_(cons) and/or the asymmetrical brakinginstruction ΔF_(cons) are determined so as to create, when they areapplied to the rudder 31 and to the differential braking assembly 27′,respectively, the steering angle of the nose gear wheel 5 being equal tothe instruction steering angle δdir_(cons), a lateral movement of theaircraft 1 according to or tending toward said instruction lateraltrajectory.

In particular, during the sub-step 350, the instruction orientationδn_(cons) and/or the asymmetrical braking orientation ΔF_(cons) aredetermined from a difference between the initial steering angleδdir_(ini) and the instruction steering angle δdir_(cons).

Preferably, the command order generated during step 340 includes anactivation or non-activation order of the differential brake 27′.

If said command order includes an activation order, the sub-step 350includes determining the instruction orientation of the rudder δn_(cons)and the asymmetrical braking instruction ΔF_(cons).

Preferably, the instruction orientation δn_(cons) and the asymmetricalbraking instruction ΔF_(cons) are determined so as to create, when theyare applied to the rudder and to the differential braking assembly 27′,respectively, the steering angle of the nose gear wheel 5 being equal tothe instruction steering angle, a lateral movement of the aircraft 1according to the instruction lateral trajectory.

If said command order includes a non-activation order, the sub-step 350includes only determining the instruction orientation δn_(cons) of therudder, to the exclusion of the asymmetrical braking instructionΔF_(cons).

Preferably, the instruction orientation δn_(cons) is then determined soas to create, when it is applied to the rudder, the steering angle ofthe nose gear wheel 5 being equal to the instruction steering angle andthe differential braking assembly 27′ being inactive, a lateral movementof the aircraft 1 according to said instruction lateral trajectory.

Step 340 also includes a sub-step 352 for sending the orientationinstruction to the rudder 31 in order to orient the rudder 31 accordingto the instruction orientation δn_(cons) and, if applicable, sending anasymmetrical braking instruction to the differential braking assembly27′ in order to apply the asymmetrical braking instruction ΔF_(cons) tosaid differential braking assembly 27′.

The control system of the present disclosure thus makes it possible tominimize the risks of loss of adhesion of the aircraft, while helpingthe pilot control various lateral movement devices.

The control system can be implemented with a command device other thanthe rudder bar 80 according to the preferred embodiment, for examplewith traditional command members such as a tiller and a rudder barmovable with two degrees of freedom.

Furthermore, the command system according to the invention may beprovided without the display assembly 54.

The embodiments and alternatives described above may further becombined.

What is claimed is:
 1. A control system of controlling a lateraltrajectory of an aircraft rolling on a runway, the aircraft including afirst set of actionable lateral movement devices, the first set ofactionable lateral movement devices including a steerable front wheel,the aircraft including a differential braking assembly of a main landinggear, the differential braking assembly being configured in order, in anactive state, to an exclusion of a nonactive state, to generate amovement of the aircraft around a yaw axis, the control systemcomprising: a rudder bar configured to be actuated by a pilot, therudder bar including a left pedal and a right pedal, each of the leftand right pedals being movable between a neutral position and anend-of-travel position along a single preset travel, a movement of theleft pedal, respectively of the right pedal, along the single presettravel, between the neutral position and a predetermined differentialbraking activation position, being configured to command a movement ofthe aircraft around the yaw axis along a first direction, respectively asecond direction opposite the first direction, by actuation of at leastone movement device of the first set, the differential braking assemblybeing in the nonactive state, a movement of the left pedal, respectivelyof the right pedal, along the single preset travel, from thepredetermined differential braking activation position toward theend-of-travel position being configured to command the movement of theaircraft around the yaw axis along the first direction, respectively thesecond direction, by actuation of at least one movement device of thefirst set, and by actuation of the differential braking assembly, thedifferential braking assembly being in the active state, the rudder barincluding a haptic feedback generator configured to apply, to each ofthe left and right pedals, a first haptic profile when the left pedal,respectively of the right pedal, is moved from the neutral position tothe predetermined differential braking activation position, and a secondhaptic profile, distinct from the first haptic profile, when the leftpedal, respectively of the right pedal, is moved from the predetermineddifferential braking activation position to the end-of-travel position.2. The control system according to claim 1, wherein the haptic feedbackgenerator is configured to apply, to each of the left and right pedals,a force opposing an actuation of each of the left pedal and the rightpedal according to a first force profile when the left pedal,respectively of the right pedal, is moved from the neutral position tothe predetermined differential braking activation position, andaccording to a second force profile, distinct from the first forceprofile, when the left pedal, respectively of the right pedal, is movedalong the single preset travel from the predetermined differentialbraking activation position to the end-of-travel position.
 3. Thecontrol system according to claim 2, wherein the haptic feedbackgenerator is configured to apply, to each of the left and right pedals,a force opposing the actuation of each of the left pedal and the rightpedal, such that a first derivative of the force opposing the actuationof the pedal from the predetermined differential braking activationposition to the end-of-travel position is strictly greater than thefirst derivative of the force opposing the actuation of the pedal to thepredetermined differential braking activation position.
 4. The controlsystem according to claim 3, wherein the first derivative of the forceopposing the actuation of the pedal from the predetermined differentialbraking activation position to the end-of-travel position is strictlygreater than any first derivative of the force opposing the actuation ofthe pedal from the neutral position to the predetermined differentialbraking activation position.
 5. The control system according to claim 1,wherein the single preset travel is a movement of the left pedal orright pedal chosen from among: a translational movement, a straight orcircular translational movement, and a rotational movement.
 6. Thecontrol system according to claim 1, wherein the single preset travel isa movement of the left pedal or right pedal according to a single degreeof freedom.
 7. The control system according to claim 1, wherein thepredetermined differential braking activation position is a preset fixedposition of the left pedal or right pedal along the single presettravel.
 8. The control system according to claim 1, further comprising aregulating module, configured to determine a threshold value of atrajectory parameter at least at one moment during a movement of theaircraft on a ground, as a function of at least one criterion chosenfrom among a piece of information relative to a current speed of theaircraft, a current runway state, an operating state of a nose gearwheel and a temperature of braking devices of the differential brakingassembly, the threshold value being representative of a first limittrajectory able to be reached by the aircraft by actuating at least onelateral movement device of the first set, the differential brakingassembly being in the nonactive state.
 9. The control system accordingto claim 8, wherein the haptic feedback generator is configured todetermine the predetermined differential braking activation position asa function of the threshold value, and to determine the first and secondhaptic profiles as a function of the predetermined differential brakingactivation position.
 10. The control system according to claim 1,further including an acquiring device for acquiring a current positionof the left pedal and a current position of the right pedal, the currentpositions being representative of an instruction lateral trajectory. 11.The control system according to claim 10, further including a trajectorycontrol module configured to, selectively: if none of the currentpositions of the left and right pedals are between the predetermineddifferential braking activation position and the end-of-travel position,send at least one input instruction to at least one lateral movementdevice of the first set, to an exclusion of the differential brakingassembly, the at least one input instruction being configured to create,when the at least one input instruction is applied to the lateralmovement devices of the first set, the differential braking assemblybeing in the nonactive state, a lateral movement of the aircraftaccording to or tending toward the instruction lateral trajectory, ifthe current position of the left pedal or right pedal is between thepredetermined differential braking activation position and theend-of-travel position, send input instructions to at least one lateralmovement device of the first set and to the differential brakingassembly, the input instructions being configured to create, when theinput instructions are applied to the lateral movement device of thefirst set and the differential braking assembly, the lateral movement ofthe aircraft according to or tending toward the instruction lateraltrajectory.
 12. The control system according to claim 1, wherein thedifferential braking assembly includes a braking device of a left mainlanding gear and a braking device of a right main landing gear, thedifferential braking assembly being configured in order, in the activestate, to the exclusion of the nonactive state, to exert, at a givenmoment, a left braking force on a left main landing gear and a rightbraking force, separate from the left braking force, on a right mainlanding gear, in order to generate the movement of the aircraft aroundthe yaw axis.
 13. The control system according to claim 1, wherein thelateral movement devices further comprise a set of electric motorsconfigured in order, in an active state, to an exclusion of a nonactivestate, to apply a speed differential between a left main landing gearand a right main landing gear to generate the movement of the aircraftaround the yaw axis, the movement of the left pedal, respectively of theright pedal, between the neutral position and the predetermineddifferential braking activation position being configured to command themovement of the aircraft around the yaw axis by actuating at least onemovement device of the first set, the differential braking assembly andthe set of electric motors being in the nonactive state, the movement ofthe left pedal, respectively of the right pedal, from the activationposition toward the end-of-travel position being configured to commandthe movement of the aircraft around the yaw axis by actuation of the atleast one movement device of the first set, and by actuation of thedifferential braking assembly and the set of electric motors, thedifferential braking assembly and the set of electric motors being inthe active state.
 14. The control system according to claim 1, furtherincluding a determination module of ground trajectories of the aircraft,configured to determine, at least at one moment: a current trajectory ofthe aircraft on the ground, including a series of waypoints predictedfor at least one element of the aircraft, under unchanged conditions ofthe lateral movement devices of the set and the differential brakingassembly, at least a first limit trajectory, including a series of firstlimit waypoints that can be reached by the at least element of theaircraft by actuating at least one of the left pedal and the right pedalbetween the neutral position and the predetermined differential brakingactivation position, and at least a second limit trajectory, including aseries of second limit waypoints that can be reached by the at least oneelement of the aircraft by actuating the left pedal or the right pedalbetween the activation position and the end-of-travel position, thecontrol system including a display assembly comprising: a viewer,configured to display a view of a runway portion located near theaircraft; and a display generating module, configured to display, on theviewer, a current trajectory curve representative of the currenttrajectory, at least a first limit curve representative of the firstlimit trajectory, and at least a second limit curve representative ofthe second limit trajectory, the curves being superimposed on the viewof the portion of the runway.